Putting It Together

Compound-Complex Sentences

A compound-complex sentence has two or more independent clauses, joined as equals, and at least one dependent clause. Here you learn to name the structure of any sentence by counting its clauses, and to draw and read a diagram with three base lines.

What you’ll learn

Classify any sentence as simple, compound, complex or compound-complex by counting its clauses
Tell a compound sentence from a compound predicate, and a clause from a verbal phrase
Draw and read a Reed-Kellogg diagram with three base lines
Find the clauses in a dependency tree from the labels conj, relcl, advcl and ccomp

The four sentence structures

Every English sentence has one of four structures. The structure depends on two counts: how many independent clauses the sentence has, and how many dependent clauses. The Practice Lab shows each sentence’s structure with the same four names.

Structure is not the same as type. The four sentence types (declarative, interrogative, imperative, exclamatory) say what a sentence does: state, ask, command or exclaim. The structure counts its clauses, so a question or a command can have any of the four structures. The word simple also names an aspect of the verb, the simple aspect, but a simple sentence can have a verb in any aspect.

Structure	Example
Simple 1 independent clause, no dependent clause	The mechanic retired.
Compound 2 or more independent clauses, no dependent clause	The mechanic retired, and I ordered tires.
Complex 1 independent clause, 1 or more dependent clauses	The mechanic who fixed my car retired.
Compound-complex 2 or more independent clauses, 1 or more dependent clauses	The mechanic who fixed my car retired, and I ordered tires.

To name the structure of a sentence, follow three steps. Worked example: When the class ended, Diego caught the bus, but Nina stayed in the library.

Count the subject-verb pairs
Each subject with its own finite verb makes one clause: the class ended, Diego caught, Nina stayed. Three pairs, so three clauses. A command has no written subject, but it still has one: the understood you.
Mark the clauses that cannot stand alone
A dependent clause usually begins with a subordinating conjunction (when, because, if), a relative pronoun (who, which, that) or a word that introduces a noun clause (that, whether). Here only When the class ended is dependent.
Look up the counts in the table
Two independent clauses and one dependent clause → compound-complex.

Three common mistakes

Two verbs with one subject make one clause. In Santiago closed his laptop and went to the gym, went has no subject of its own: it shares Santiago. The sentence is simple, with a compound predicate. Spanish school grammar often counts one clause for each conjugated verb (cerró, se fue); English counts subject-verb pairs.
A verbal phrase is not a clause. In Marta stayed late to help her brother, the phrase to help her brother has no subject and no tense, so the sentence is simple. See verbal phrases.
A clause without that can still be dependent. Spanish almost always keeps que, but English often leaves that out. In The song Nina wrote won a prize, it is left out before Nina wrote; in Omar says the museum opens at nine, before the museum opens. Both sentences are complex.

Drawing and reading three base lines

A compound-complex diagram uses only lines you already know. Draw it in three steps. To read it, take one base line at a time.

Give each clause its own base line
The sentence below has three clauses, so its diagram has three base lines.
Join the independent clauses with a step-down
Put them one above the other. A dashed step-down joins their verbs and carries the conjunction (and), as in compound sentences.
Attach each dependent clause
An adjective clause hangs from its noun on a dashed line: here from mechanic to who, as in Adjective Clauses. An adverb clause hangs from the word it modifies, usually the verb, and a noun clause stands on a pedestal in the slot it fills.

“The mechanic who fixed my car retired, and I ordered new tires.”

Reed-Kellogg — three base lines, two kinds of connector

det Determiner
nsubj Nominal subject
relcl Relative clause modifier
poss Possession modifier
dobj Direct object
ROOT Root of the sentence
cc Coordinating conjunction
conj Conjunct
amod Adjectival modifier

Dependency — ordered hangs from retired as conj; fixed hangs from mechanic as relcl

Comparing the two views

Reed-Kellogg gives each clause its own base line: three lines, three clauses. A dashed step-down joins the two equal clauses, and a dashed line from mechanic to who attaches the dependent one. The tree has one root, retired, so ordered hangs below it even though the two clauses are equals. The labels show the relationship instead: conj for an equal clause, relcl for a dependent one.

How to find the clauses in each view:

Diagram: each base line that a full vertical line divides into a subject and a verb is a clause. A verbal phrase never gets that full vertical, because its verb is not finite, even when it has a subject of its own. A clause that hangs from a word on a dashed line, or stands on a pedestal, is dependent. The others are independent, and step-downs join them.
Tree: conj joins equals, so a conj verb with its own nsubj starts a clause of the same kind as the clause it hangs from. Here ordered (subject I) hangs from the root, retired, so it starts a second independent clause. A conj verb with no subject of its own belongs to a compound predicate and adds no clause.
Tree: a finite verb with its own subject that hangs by relcl, advcl or ccomp heads a dependent clause (fixed, subject who). A verbal can carry these labels too, but it heads a verbal phrase, not a clause: in Marta stayed late to help her brother, the infinitive help is advcl. That is true even when the verbal has an nsubj: in Omar wants his sister to drive, drive is a ccomp with the subject sister, but it is still an infinitive.

Each label has its own entry: conj, relcl, advcl and ccomp.

The Reed-Kellogg marks, in one list

Every mark the earlier pages taught, and the page that teaches each one.

Base line, full vertical, half vertical, backslash — Reed-Kellogg Diagrams
Slants for modifiers, chained for modifiers of modifiers — Articles, Adjectives & Objects, Adverbs
Diagonal-and-horizontal for prepositional phrases — Prepositional Phrases
Pedestals for constructions filling one slot — Gerunds, Infinitives, Noun Clauses
Chevrons for coordination — Imperatives & Conjunctions
A dashed step-down between independent clauses — Imperatives & Conjunctions
Dashed lines for subordination — Adverb Clauses, Adjective Clauses
Floating lines for elements outside the clause — disjuncts and vocatives

Quick check

What is the structure of this sentence? Nina finished her shift and drove to the station.
Answer
Simple. It has one subject, Nina, and two verbs that share it, finished and drove. Two verbs with one subject form a compound predicate, so the sentence has one independent clause and no dependent clause.
How many clauses does this sentence have, and what is its structure? Omar wants to study medicine, but his parents hope that he will choose law.
Answer
Three clauses: two independent and one dependent, so the sentence is compound-complex. Omar wants… and his parents hope… are independent clauses joined by but. The noun clause that he will choose law is dependent: it starts with that and has its own subject, he. The phrase to study medicine is not a clause: it is an infinitive phrase, with no subject and no tense.
The Reed-Kellogg diagram of Priya baked a cake that everyone loved, but Omar preferred the bread has three base lines. A dashed step-down with but on it joins two of them, and the third hangs from cake on a dashed line. Which base lines are independent clauses?
Answer
The two that the step-down joins: Priya baked cake and Omar preferred bread. A step-down joins equals, and each of them can stand alone. The line that hangs from cake (everyone loved that) is a dependent adjective clause, so the sentence is compound-complex.
Look at the dependency tree of Marta cooked dinner while Diego washed the dishes, and their son set the table. The verb set hangs from cooked as conj and has its own nsubj, son. The verb washed hangs from cooked as advcl and has its own nsubj, Diego. What is the structure?
Answer
Compound-complex. The verb set is a conj verb with its own subject, and it hangs from the root, so their son set the table is a second independent clause. The verb washed is an advcl verb with its own subject, so while Diego washed the dishes is a dependent adverb clause. Two independent clauses and one dependent clause make a compound-complex sentence.

Key terms

Independent clause: A clause that can stand alone as a sentence. Every sentence has at least one. The Roles exercise boxes it as a Main clause, with any clause that depends on it inside. The sun rose. We packed the car, and the dog jumped in. — two of them, joined.
See: Grammar Basics
Simple sentence: One independent clause and no dependent clause. Two verbs that share one subject are still one clause. Our train left on time. Diego ironed his shirt and left for work.
See: Coordination
Compound sentence: Two or more independent clauses joined as equals. Stacked base lines with a step-down. Marta sang, and Diego played the guitar. The bus was late, but we arrived on time.
See: Imperatives & Conjunctions
Complex sentence: One independent clause plus at least one dependent clause. Nobody answered when Omar knocked. The man who sold us the tickets was friendly.
See: Adverb Clauses
Compound-complex sentence: Two or more independent clauses plus at least one dependent clause. Its diagram has a step-down between the equal clauses and a dashed line or a pedestal for each dependent clause. We left because it rained, and the dog followed us. She kept the letter that he sent, but she never replied.

Practice on a real sentence

A compound-complex sentence with three verbs. In it, little wiser means not much wiser. Before you start, find the three verbs and decide which one heads a clause that cannot stand alone. In the Roles tab, box each independent clause as a Main clause; in the Dependencies tab, look for conj and relcl. If you already worked on this sentence on another page, press Restart to try it again.

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