Practice & Reference

Glossary

Every term the Learn section defines, in one alphabetical list — 133 of them. Each entry gives the short definition and links to the page that teaches it, where the examples are set in context. For the codes themselves — the seventeen part-of-speech categories, the fifty Penn tags and the forty-six dependency labels — use the two reference indexes instead.

A

A line with no connection: A short horizontal floating above the diagram, attached to nothing. It marks an element standing outside the clause’s grammar altogether: a person being addressed, or an adverb commenting on the whole sentence. Children, we must hurry. — Children floats above the clause. Frankly, the plan failed. — so does frankly.
Read it in context: Reed-Kellogg Diagrams
Adjectival phrase: A prepositional phrase modifying a noun. Hangs from that noun. The letter from Melvin arrived. The path along the river floods.
Read it in context: Prepositional Phrases
Adjective: A word describing a noun. Attributive adjectives sit next to the noun and hang on a slant; predicate adjectives arrive through a linking verb and sit on the base line. The tired hikers rested. — attributive. The hikers were tired. — predicate.
Read it in context: Articles, Adjectives & Objects
Adjective clause: A dependent clause modifying a noun. Also called a relative clause. Relation relcl. The violin that she inherited needs strings. We met the guide who found the trail.
Read it in context: Adjective Clauses
Adjective phrase: An adjective together with what it carries — a prepositional phrase, an infinitive — set off from the noun it describes. Drawn on a slant beneath that noun, like any adjective. Relation advcl when it comes first in the sentence. Weary from the hike, Mia slept. Eager to help, the boys carried the bags.
Read it in context: Articles, Adjectives & Objects
Adjunct: An optional element you can delete without breaking the sentence. Adjuncts hang below the base line. Birds sing at dawn. — remove at dawn and the sentence still stands. Yesterday the kettle broke. — yesterday is an adjunct too.
Read it in context: Grammar Basics
Adverb: A word modifying a verb, adjective or adverb. Tagged RB (or RBR/RBS for comparative and superlative), relation advmod. She spoke softly. — on a verb. She spoke too softly. — on another adverb. a very old map — on an adjective.
Read it in context: Adverbs
Adverb clause: A dependent clause doing an adverb’s job. Relation advcl. We left because it rained. When the bell rang, everyone stood.
Read it in context: Adverb Clauses
Adverbial: Anything doing an adverb’s job — a single word, a prepositional phrase, or a whole clause. All three hang below the word they modify. She left early. She left at dawn. She left when the bell rang. — a word, a phrase and a clause.
Read it in context: Adverbs
Adverbial clause: A clause modifying a verb, labelled advcl on its own verb and normally introduced by a mark. We left because it rained. When the bell rang, everyone stood.
Read it in context: Modifier Relations
Adverbial objective: A noun phrase answering an adverb’s question. Relation npadvmod, drawn below the verb. We waited an hour. She walked home.
Read it in context: Adverbial Objectives & Retained Objects, Modifier Relations
Adverbial phrase: A prepositional phrase modifying a verb, adjective or adverb. Hangs from that word. She sat on the chair. He runs before breakfast.
Read it in context: Prepositional Phrases
Affix: A prefix or suffix split from its stem — the co of co-captains. Only ever AFX by administrator correction. Two students were made co-captains. The pre-war house survived.
Read it in context: Numbers, Symbols & the Rest
Agent: The doer in a passive sentence, named in a by phrase. Relation agent. The road was flooded by the storm. The letter was signed by the mayor.
Read it in context: Miscellaneous
Antecedent: The noun the relative pronoun refers back to — the one the clause modifies. The violin that she inherited — violin is the antecedent of that. The guide who found the trail — guide is the antecedent of who.
Read it in context: Adjective Clauses
Appositive: A noun renaming the noun beside it. Written in parentheses in the diagram; relation appos. My friend Jacob called. The capital, Lima, is on the coast.
Read it in context: Possessives & Appositives, Nominal Dependents
Arc: One head-to-dependent link, carrying a relation label. The Dependencies exercise asks you to identify the ordered triple: relation, head, dependent. Birds sing. has one arc, nsubj, from sing to birds. Birds sing loudly. has two; the second is labelled advmod.
Read it in context: Dependency Parsing
Argument: An element the verb requires: a subject, a direct object, an indirect object, a complement. Arguments sit on the base line. Birds eat seeds. — drop either noun and the sentence breaks. She gave him a map. — gave needs both.
Read it in context: Grammar Basics
Article: a, an, the. A kind of determiner, drawn on a slant like any other modifier. Tagged DT. A kestrel caught the vole. An owl hooted.
Read it in context: Articles, Adjectives & Objects
Attributive adjective: An adjective before its noun — a tiny weed. Drawn on a slant under the noun. A tiny weed grew. The old map tore.
Read it in context: Adjectives & Adverbs
Auxiliary: Any helping verb: the modals, plus be, have and do when they support a main verb rather than being one. She has finished. — has helps finished. She has a car. — here has is the main verb, not an auxiliary.
Read it in context: Modal Auxiliaries, Verbs & Auxiliaries, Function Word Relations

C

Cardinal number: A counting number — three, 42. NUM/CD. Ordinals (third) are adjectives. Three boats sank. Tickets cost 42 dollars.
Read it in context: Numbers, Symbols & the Rest
ccomp: “Clausal complement” — a clause completing a verb, with its own subject. Contrast xcomp, whose subject comes from the main clause. Everyone knows that the ferry left. — left is the ccomp of knows. She said that the bridge closed.
Read it in context: Noun Clauses
Chevron (a fork): The base line splits into two or more parallel branches that rejoin. It means coordination: two subjects, two verbs or two objects sharing everything else. The conjunction sits on a dashed line between the branches. Jack and Jill fell. — two subjects fork before one verb. She washed and dried the plates. — one subject, two verbs.
Read it in context: Reed-Kellogg Diagrams
Clause: A group of words containing a subject and a verb. An independent clause can stand alone as a sentence; a dependent (subordinate) clause cannot. The sun rises. is an independent clause. when the sun rises has a subject and a verb too, but it leaves you waiting — a dependent clause.
Read it in context: Grammar Basics
Closed class: A word class with a fixed membership — determiners, prepositions, conjunctions, particles. The parser looks the word up and then decides which of its jobs it is doing. The kettle sat on the stove. — the and on belong to closed classes. She left because it rained. — so does because.
Read it in context: Determiners & Function Words
Common noun: A noun that names a kind of thing rather than one particular thing — river, courage. NN when singular or mass, NNS when plural. The river flooded. Courage matters.
Read it in context: Nouns & Pronouns
Complement: Any element completing the meaning of a verb. Required, so it sits on the base line rather than below it. She became a pilot. We elected her captain. — neither sentence survives without its complement.
Read it in context: Indirect Objects & Complements, Core Arguments
Complex sentence: A sentence with one independent clause and at least one dependent clause. We left because it rained. The violin that she inherited needs new strings.
Read it in context: Adverb Clauses, Compound-Complex Sentences
Compound: A noun used to modify another noun. Distinguished from amod purely by the modifier’s part of speech — see Parts of Speech. The kitchen door stuck. A philosophy professor spoke.
Read it in context: Nominal Dependents
Compound element: Two or more subjects, verbs or objects sharing the rest of the clause. Drawn as a fork on one base line. Jack and Jill fell. — two subjects. She bought apples and pears. — two objects.
Read it in context: Imperatives & Conjunctions
Compound predicate: Two verbs sharing one subject. Labelled with conj exactly like a compound sentence — the difference is whether the second verb has its own nsubj. She washed and dried the plates. The dog barked and ran.
Read it in context: Coordination
Compound sentence: Two independent clauses joined by a conjunction. Drawn as two base lines with a dashed step-down between them. She knocked, and the door opened. We waited, but nobody came.
Read it in context: Imperatives & Conjunctions, Compound-Complex Sentences
Compound-complex sentence: Two or more independent clauses plus at least one dependent clause. Both connectors in one diagram. We left because it rained, and the dog followed us. She kept the letter that he sent, but she never replied.
Read it in context: Compound-Complex Sentences
Conjunct: One of the things being joined. The first is promoted to head of the whole coordination; the rest are labelled conj. Jack and Jill fell. — Jill is the conj of Jack. She washed and dried the plates.
Read it in context: Coordination
Constituency: The view of a sentence as nested groups of words, each group doing one job. This is what a Reed-Kellogg diagram draws. The tired birds slept. is [the tired birds] + [slept], with [tired] nested inside the first group. Birds sing at dawn. is [birds] + [sing at dawn].
Read it in context: Grammar Basics
Coordinating conjunction: and, but, or, nor, for, so, yet — the words that join equals. Tagged CC, and always cc in the tree. Tea or coffee? She tried, but the door stuck.
Read it in context: Imperatives & Conjunctions, Coordination
Copula (linking verb): be joining a subject to a description — Marta is a pilot. Tagged AUX by this model even though it is the only verb present. The soup is cold. Marta is a pilot.
Read it in context: Verbs & Auxiliaries
Core argument: Something a predicate requires rather than merely permits. Deleting it breaks the sentence instead of shortening it. Birds eat seeds. — drop seeds and the sentence breaks. She became a pilot.
Read it in context: Core Arguments
Correlative pair: A two-part conjunction such as either…or. The leading half is preconj; the middle half stays cc. Either the ferry or the bus will do. Both Jack and Jill fell.
Read it in context: Coordination
Crossing arcs: When a dependent sits far from its head, arcs cross. Not an error — a consequence of keeping the words in sentence order. A letter arrived that changed everything. — the clause belongs to letter but follows arrived, so its arc crosses. She looked the word up. — up belongs to looked, across the word.
Read it in context: Dependency Parsing
csubj: “Clausal subject” — the relation when a whole construction, rather than a single noun, is the subject. Rescuing the kitten took an hour. — Rescuing is the csubj of took. Whoever arrives first will unlock the door.
Read it in context: Gerunds

D

Dangling participle: A participial phrase with no noun in the sentence for it to modify. A writing error, not a diagramming one. Walking home, the rain started. — the rain was not walking. Having finished the exam, the pencils were collected.
Read it in context: Participles
Dashed line: A connection that is grammatical rather than structural — it joins two things without either being part of the other. Subordinating conjunctions, relative pronouns and coordinating conjunctions all travel on dashed lines. We left because it rained. — because runs on a dashed line down to its clause. The book that you lent me is here. — that is joined to book the same way.
Read it in context: Reed-Kellogg Diagrams
Declarative sentence: A sentence that states something, with the subject before the verb and a full stop at the end. The ferry leaves at noon. Our neighbours keep bees.
Read it in context: Sentence Types & Voice
Degree: Positive, comparative or superlative — long, longer, longest. The only thing the fine tag adds to an adjective or adverb. This road is longer. That road is the longest.
Read it in context: Adjectives & Adverbs
Dependency: The view of a sentence as a set of labelled word-to-word links. This is what the dependency tree draws, and what the parser actually computes. In Birds sing. the one link runs from sing to birds (nsubj). In The tired birds slept. every word links to exactly one other.
Read it in context: Grammar Basics
Dependent: The word doing the depending — the arrow points at it. Birds sing. — birds is the dependent of sing. Birds sing loudly. — loudly is a second dependent of the same verb.
Read it in context: Dependency Parsing
Dependent clause: A clause that cannot stand alone. The three kinds are adverb, adjective and noun clauses, named for the job they do. We left because it rained. The violin that she inherited needs strings. — each clause has a subject and a verb, and neither can be a sentence by itself.
Read it in context: Adverb Clauses
Determiner: A word that introduces a noun phrase and fixes its reference. DT, WDT or PDT. The kettle whistled. Which road floods? Both my parents sing.
Read it in context: Determiners & Function Words
Direct address: Naming the person spoken to. Grammatically outside the clause — which is why a Reed-Kellogg diagram floats it on its own line above the base line. Children, we must hurry. Pass the salt, Maria.
Read it in context: Root & Leftovers
Direct object: The noun receiving the action. On the base line, after a half vertical. Relation dobj. A kestrel caught a vole. She bought apples. — ask “caught what? bought what?”.
Read it in context: Articles, Adjectives & Objects
Disjunct: An adverb commenting on the whole sentence rather than modifying anything in it. Drawn floating above the clause, unconnected. Frankly, the plan failed. Luckily, nobody was hurt.
Read it in context: Adverbs
Ditransitive verb: A verb taking both a direct and an indirect object — give, send, tell, show, offer. She sent him a letter. They offered us seats.
Read it in context: Indirect Objects & Complements

E

Ellipsis: Words omitted because they can be recovered from context. Neither notation represents them well. She can sing, and he can too. — sing is left out after the second can. Some left early, others late. — left is left out.
Read it in context: Miscellaneous
Exclamatory sentence: A sentence that expresses strong feeling and ends in an exclamation mark, often starting with what or how. What a long day this was! How quickly the summer passed!
Read it in context: Sentence Types & Voice
Existential there: The there of there is. A placeholder subject, tagged EX, with PRON as its coarse category. There is a bird in the yard. There were no seats left.
Read it in context: Nouns & Pronouns
Expletive: A word filling a grammatical slot without contributing meaning. There as a placeholder subject is the standard case; relation expl. There is a bird in the yard. There were no seats left.
Read it in context: Adverbial Objectives & Retained Objects, Function Word Relations

F

Fallback label: dep, used when no other relation fits. On well-formed English it is a sign of a parse problem rather than a genuine analysis. Um, the thing, uh, broke. — filler words are where it tends to turn up. Yes, well, no. — so is a string of words with no structure to hang on.
Read it in context: Root & Leftovers
Finite form: A form that carries tense and agrees with a subject — VBD, VBP, VBZ. The base form and the participles are non-finite. She sings. — VBZ. They sang. — VBD. They want to sing. — VB, non-finite.
Read it in context: Verbs & Auxiliaries
Finite verb: A verb inflected for tense that can head a clause by itself. Contrast the non-finite forms, which cannot. The kettle whistles. — present tense. The kettle whistled. — past tense; either one heads the clause alone.
Read it in context: Grammar Basics, Subjects & Verbs
Function word: A word carrying grammatical rather than lexical meaning. Determiners, auxiliaries, markers and particles. The kettle had whistled. — a determiner and an auxiliary. We left because it rained. — a marker.
Read it in context: Function Word Relations

G

Gerund: An -ing verb form used as a noun. Tagged VBG, same as a participle — the tag does not distinguish them, only the relation does. Swimming keeps her fit. He enjoys cooking.
Read it in context: Gerunds
Gerund phrase: The gerund plus its own objects and modifiers, filling one noun slot together. Rescuing the kitten took an hour. She dislikes waiting in queues.
Read it in context: Gerunds

H

Head: The essential word in a phrase — the one that survives when you delete the others. In a dependency parse, every word except the root has exactly one head. In the tired birds the head is birds; in very tired birds it is tired.
Read it in context: Grammar Basics, Dependency Parsing

I

Imperative: A command. Its subject is an understood you, written in parentheses in the diagram and absent from the dependency tree entirely. Shut the door. Please wait here. — in both, the doer is the person addressed.
Read it in context: Imperatives & Conjunctions
Imperative sentence: A command or request. The subject you is left unsaid and the verb is in its base form. Shut the window. Please hand me the map.
Read it in context: Sentence Types & Voice
Independent clause: A clause that can stand alone as a sentence. Every sentence has at least one. The sun rose. We packed the car, and the dog jumped in. — two of them, joined.
Read it in context: Compound-Complex Sentences
Indirect object: Who or what receives the direct object. On a horizontal beneath the verb; relation dative. She gave Luis a postcard. Show me the map.
Read it in context: Indirect Objects & Complements, Core Arguments
Infinitive: to plus a base verb. Carries no tense, so it cannot head a clause. The to is tagged TO, relation aux. She wants to leave. To forgive takes courage.
Read it in context: Infinitives
Infinitive phrase: The infinitive plus its own objects and modifiers, all travelling together as one unit. She wants to leave early. To climb that hill takes an hour.
Read it in context: Infinitives
Intensifier: An adverb that only scales another word — very, rather, quite. Always RB. The soup is very hot. She left rather early.
Read it in context: Adjectives & Adverbs
Interjection: An exclamation outside the sentence’s grammar — oh, wow, please. INTJ/UH. Oh, the ferry left. Please hand me the map.
Read it in context: Numbers, Symbols & the Rest
Interrogative sentence: A question. An auxiliary or a question word comes before the subject, and the sentence ends in a question mark. Did the ferry leave on time? Where does the ferry stop?
Read it in context: Sentence Types & Voice
Inversion: Moving an auxiliary in front of the subject to form a question. Undone in the Reed-Kellogg diagram, preserved in the dependency tree. She can swim. → Can she swim? They have left. → Have they left?
Read it in context: Modal Auxiliaries

L

Lemma: The dictionary form of a word: watched → watch, foxes → fox. Stored for every word, though no exercise asks for it. The foxes watched us. has the lemmas the, fox, watch, we. She is running late. has she, be, run, late.
Read it in context: Parts of Speech
Level: Distance from the root, which is what fixes a word’s vertical position. Computed once from the whole parse, so the tree never reflows as you answer. Birds sing. — sing is level 0, birds level 1. The tired birds slept. — the and tired sit at level 2, one row below birds.
Read it in context: Dependency Parsing
Linking verb: A verb connecting the subject to a description of itself rather than acting on something. be, become, seem, feel, look, smell, sound, taste, remain. The soup smells wonderful. She became a pilot.
Read it in context: Subjective Complements

M

Main verb: The verb that carries the clause’s meaning. VERB on the coarse scale, whatever its form. She has a car. — has is the main verb. She has finished. — now it is finished.
Read it in context: Verbs & Auxiliaries
Mass noun: An uncountable noun — sand, happiness. Tagged NN like a singular, because it behaves like one. Sand filled her shoes. She wished us happiness.
Read it in context: Nouns & Pronouns
Modal auxiliary: One of nine verbs — can, could, may, might, must, shall, should, will, would — that add possibility, obligation or prediction. Tagged MD, and always aux in the tree. You must leave now. It might rain later.
Read it in context: Modal Auxiliaries
Modifier: A word or phrase that adds detail to another word without being required by it. Drawn on a slanted line beneath the word it modifies. The tired birds slept. — tired modifies birds. Birds sing loudly. — loudly modifies sing.
Read it in context: Grammar Basics, Modifier Relations
Morphology: The grammatical features derived from the fine tag — Tense=Past, Number=Sing. Derived rather than stored independently, which is why correcting a tag corrects the morphology too. She sings. — VBZ gives Tense=Pres and Person=3. They sang. — VBD gives Tense=Past.
Read it in context: Parts of Speech

N

Nominative absolute: A noun and a participle forming a small clause of their own, attached to nothing in the main sentence. Drawn floating above the clause. The rain having stopped, we walked home. Her voice trembling, Nora read the letter.
Read it in context: Participles
Non-finite verb: An infinitive, gerund or participle — a verb form carrying no tense, which needs a finite verb elsewhere in the sentence to anchor it. The kettle began to whistle. — an infinitive, anchored by began. The whistling kettle woke us. — a participle, anchored by woke.
Read it in context: Grammar Basics
Noun clause: A dependent clause filling a noun slot. Relation ccomp when it completes a verb, csubj when it is the subject. Everyone knows that the ferry left. — object. Whoever arrives first will unlock the door. — subject.
Read it in context: Noun Clauses
Noun phrase: A noun together with everything hanging beneath it. Never drawn as a boundary in a dependency tree — you read it off the subtree. The old kettle whistled. She bought a map of the coast.
Read it in context: Nominal Dependents

O

Object of the preposition: The noun phrase the preposition governs — the sofa, not just sofa. Drawn on the horizontal, with its modifiers slanting below. In the dependency view the relation pobj sits on the head noun alone; the phrase is that word plus everything hanging from it. She sat on the sofa. A letter from my aunt arrived.
Read it in context: Prepositional Phrases
Objective complement: The mirror image: a word completing the object rather than the subject. Same backslash, different anchor. They painted the fence white. We elected her captain.
Read it in context: Subjective Complements, Indirect Objects & Complements
Open clause: A subordinate clause with no subject of its own, borrowing one from the clause above. The reason xcomp is called an open clausal complement. She wants to leave. — she is understood as the one leaving. They began to sing.
Read it in context: Core Arguments
Original value: The parser’s first prediction, kept permanently even after an administrator overrides it. Exercises always grade the live value, never this one. Children, we must hurry. — the parser said npadvmod; the live value is vocative. Two students were made co-captains. — NN on co, corrected to AFX.
Read it in context: Root & Leftovers

P

Participial phrase: A participle with its own objects and modifiers, all modifying one noun. Sitting in the corner, the boys laughed. Boxes stacked in the closet fell.
Read it in context: Participles
Participle: A verb form that can also modify a noun. Present participle VBG, past participle VBN. The whistling kettle woke us. The broken vase lay on the floor.
Read it in context: Verbs & Auxiliaries
Particle: Part of a phrasal verb, labelled prt. Distinguished from a preposition by having no object of its own. The plane took off. She looked the word up.
Read it in context: Function Word Relations
Past participle: The -ed/-en form used as an adjective. Tagged VBN. Also the form used in the perfect and passive. The broken vase lay on the floor. Boxes stacked in the closet fell.
Read it in context: Participles
Pedestal: The stand raising a whole construction into a single slot. Used for infinitives, gerunds and noun clauses alike. To forgive takes courage. — the infinitive subject stands on a pedestal. She likes to swim. — so does an infinitive object.
Read it in context: Infinitives, Noun Clauses
Pedestal (a stand): A small triangle or stem lifting something above the base line. It means “this whole construction is filling a single slot” — a gerund phrase acting as a subject, or a clause acting as an object. Swimming keeps her fit. — the gerund stands on a pedestal in the subject slot. She knows that we left. — the whole clause stands on one in the object slot.
Read it in context: Reed-Kellogg Diagrams
Personal pronoun: I, you, he, she, it, we, they and their object and reflexive forms. All PRP; the case is recorded by the dependency label, not the tag. She called him. We found it ourselves.
Read it in context: Nouns & Pronouns
Phrasal verb: A verb plus a particle acting as one unit — take off, give up. The particle is RP. The plane took off late. She looked the word up.
Read it in context: Determiners & Function Words
Phrase: A group of words acting as a single unit, with no subject-and-verb pair of its own. the tired birds, at night, had been waiting. The tired birds slept. — the first three words fill the subject slot together.
Read it in context: Grammar Basics
POS (coarse): The seventeen-value Universal Dependencies category. Language-independent, and what the syntactic diagrams are built from. The kettle whistled. — DET, NOUN, VERB. She left quickly. — PRON, VERB, ADV.
Read it in context: Parts of Speech
Possessive: A noun or pronoun marking ownership. Relation poss; the apostrophe-s is a separate token with relation case. Omar’s coat is here. The teacher’s handwriting slants.
Read it in context: Possessives & Appositives
Possessive pronoun: my, your, her, its, our, their. Tagged PRP$, and drawn on a slant like any other possessive. Her coat is here. They lost their map.
Read it in context: Possessives & Appositives
Possessor: Labelled poss, and attached to the thing owned. A ’s is a separate token carrying its own case arc. Omar’s coat is here. Her coat is here.
Read it in context: Nominal Dependents
Predicate: What the clause says about its subject: the verb plus everything travelling with it. It sits right of the full vertical line. Birds sing. — just the verb. The kettle whistled on the stove. — the verb and its phrase.
Read it in context: Grammar Basics, Subjects & Verbs
Predicate adjective: An adjective completing a linking verb and describing the subject. Relation acomp. The soup smells wonderful. The road was icy.
Read it in context: Subjective Complements, Adjectives & Adverbs
Predicate nominative: A noun completing a linking verb and renaming the subject. Relation attr. She became a pilot. My brother is an engineer.
Read it in context: Subjective Complements
Preposition: A word relating a noun to the rest of the sentence. Tagged IN, relation prep. Coarse category ADP. She sat on the chair. We walked through the park after lunch.
Read it in context: Prepositional Phrases, Determiners & Function Words
Present participle: The -ing form used as an adjective. Tagged VBG — identical to a gerund, so the tag alone cannot tell you which it is. The whistling kettle woke us. People sitting in the corner laughed.
Read it in context: Participles
Proper noun: A name. Capitalised in English, and the capital is the parser’s main clue. NNP singular, NNPS plural. Marta flies for Avianca. The Alps were snowy.
Read it in context: Nouns & Pronouns

R

Relative clause: A clause modifying a noun, where the noun also has a role inside the clause. Labelled relcl; the relative pronoun may be absent. The violin that she inherited needs strings. The letter you sent arrived. — no pronoun at all.
Read it in context: Modifier Relations
Relative pronoun: who, whom, whose, which, that — introduces the clause and simultaneously fills a slot inside it. The violin that she inherited — that is the object of inherited. The guide who found the trail — who is its subject.
Read it in context: Adjective Clauses
Restrictive clause: A clause narrowing down which one is meant, written without commas. A non-restrictive clause adds detail and takes commas. The violin that she inherited needs strings. — restrictive: it says which violin. My violin, which she inherited, needs strings. — non-restrictive: it adds detail about a violin already identified.
Read it in context: Adjective Clauses
Retained object: The object left behind when a two-object verb goes passive and the other object becomes the subject. She was given a medal. — medal stays an object. We were told the truth.
Read it in context: Adverbial Objectives & Retained Objects
Root: The one word with no head, stored as being its own head. Almost always the main verb. Birds sing. — the root is sing. The kettle had been whistling. — the root is whistling, not either auxiliary.
Read it in context: Dependency Parsing, Root & Leftovers

S

Sentence normalisation: The cleaning every submitted sentence gets before parsing: trimmed, internal whitespace collapsed, clitic apostrophes straightened. It is why _SP is impossible here. The ferry leaves at noon. typed with two spaces inside is stored with one. Omar’s coat is here. typed with a curly apostrophe is stored with a straight one.
Read it in context: Numbers, Symbols & the Rest
Shared object: One direct object belonging to two coordinated verbs. Invisible to the parser, so it is marked by hand. Barbara mowed and watered the lawn. He washed and dried the plates.
Read it in context: Miscellaneous
Subject: What the clause is about — the answer to who? or what? in front of the verb. It sits left of the full vertical line. Birds sing. The old kettle whistled. — the subject can be one word or a whole phrase.
Read it in context: Grammar Basics, Subjects & Verbs
Subordinating conjunction: The word introducing a dependent clause. Coarse category SCONJ, relation mark. We left because it rained. Although it was late, she kept reading.
Read it in context: Adverb Clauses, Determiners & Function Words
Subordinator: that, whether, if — introduces the clause with no job inside it. Relation mark. Everyone knows that the ferry left. Ask whether the shop is open.
Read it in context: Noun Clauses
Symbol: A meaningful non-word character — $, x between numbers. Unevenly recognised; the percent sign is a noun to this model. Tickets cost $12. The room is 3 x 4 metres.
Read it in context: Numbers, Symbols & the Rest

T

TAG (fine): The Penn Treebank label — English-specific, and carrying the tense, number and degree information the coarse category throws away. This is what the Tags exercise asks for. The kettle whistled. — DT, NN, VBD: a singular noun and a past-tense verb. Kettles whistle. — NNS, VBP.
Read it in context: Parts of Speech
Token: One unit as the parser counts them — usually a word, but a contraction splits into two (can’t is ca + n’t) because the halves behave differently. We can’t stay. has four tokens but three words. Omar’s coat is here. has five tokens: Omar and ’s are counted separately.
Read it in context: Grammar Basics
Token split: The parser stores Omar’s and can’t as two units each, because their halves behave differently. They are drawn joined and clicked separately. Omar’s coat is here. — five tokens. We can’t stay. — four.
Read it in context: Possessives & Appositives
Transitive verb: A verb that takes a direct object. One that does not is intransitive; many English verbs are both, depending on the sentence. She bought apples. — transitive. She slept. — intransitive. She read the letter. and She read all night. — the same verb both ways.
Read it in context: Articles, Adjectives & Objects
Transitivity: How many objects a verb takes in a given sentence: none, one, or two. She slept. — none. She read the letter. — one. She gave him the letter. — two.
Read it in context: Miscellaneous

U

Understood subject: The you a command implies but does not say, written (x) in a Reed-Kellogg diagram. In Wait here. the understood subject is you; in Please hand me the map. it is you again.
Read it in context: Sentence Types & Voice

V

Verb phrase: The main verb plus its auxiliaries, occupying one slot on the base line however many words it contains. She had been waiting. — three words, one slot. They will have finished by noon.
Read it in context: Modal Auxiliaries
Verbal: A verb form used as another part of speech. The three are infinitives, gerunds and participles. She wants to leave. — an infinitive. Swimming keeps her fit. — a gerund. The whistling kettle woke us. — a participle.
Read it in context: Gerunds
Vocative: The person being addressed. Grammatically outside the clause, so it floats on an unconnected line above the diagram. Maria, pass the salt. We are ready, everyone.
Read it in context: Imperatives & Conjunctions
Voice: Whether the subject performs the action (active) or receives it (passive). Active: The storm flooded the road. Passive: The road was flooded by the storm.
Read it in context: Sentence Types & Voice, Subjects & Verbs

W

Word: The smallest unit that can stand on its own and be moved around a sentence. Every word belongs to a part-of-speech category. Birds sing loudly. is three words from three categories; the tired birds is three words doing the job of one.
Read it in context: Grammar Basics

X

xcomp: “Open clausal complement” — the relation for an infinitive completing another verb, with its subject supplied by the main clause. She wants to leave. — leave is the xcomp of wants. They began to sing.
Read it in context: Infinitives