Dependency Relations

Coordination

Three relations for words and clauses joined by and, but, or and similar words. Coordination joins equals, but a dependency tree must make one of them the head. This page shows which one, and how the other words attach to it.

What you’ll learn

Explain why a dependency tree must make one conjunct the head
Attach cc and conj to the first conjunct, not to that conjunct’s head
Find the head of each conj in a list of three or more
Label the first word of either…or, neither…nor and both…and as preconj
Tell a coordinating conjunction (cc) from a subordinating marker (mark)

The first conjunct becomes the head

In salt and pepper, the two nouns are equals: neither depends on the other. Each joined part is a conjunct. A dependency tree cannot show two equals. Every arc in it goes from a head to a dependent, and every word has exactly one head.

So the tree follows a fixed rule: it makes the first conjunct the head of the whole coordination. The first conjunct then takes the role of the whole group in the sentence.

Find the conjunction
In Salt and pepper sat nearby, the conjunction is and.
Find the conjuncts
and joins Salt and pepper. The first one, Salt, becomes the head of the group.
Give the first conjunct the group's role
The group is the subject of sat, so Salt is the nsubj of sat.
Attach the rest to the first conjunct
and is the cc of Salt, and pepper is the conj of Salt. Neither one attaches to sat.

“Salt and pepper sat nearby.”

nsubj Nominal subject
cc Coordinating conjunction
conj Conjunct
ROOT Root of the sentence
advmod Adverbial modifier

'Salt' takes the nsubj arc; 'and' and 'pepper' both attach to 'Salt'

The three relations

cc Coordinating conjunction

The coordinating conjunction itself: and, but, or, nor or yet. It attaches to the conjunct just before it, so in a pair it attaches to the first conjunct.

How the parser decides: the word is a coordinating conjunction between two conjuncts. School grammar lists seven, the FANBOYS: for, and, nor, but, or, yet, so. The parser reads two of them differently: for between two clauses is a mark, like because, and so is an advmod.

With so, the parser also makes the first clause depend on the second. In It rained, so we stayed home, rained is a ccomp of stayed, the root. Between two adjectives, yet is often an advmod too, not a cc: small yet bright.

Every word that takes cc

and, or, but, nor, yet
The signs and short forms &, + and and/or, and plus and minus between two numbers
The last word of as well as: in bread as well as milk, the second as is the cc, and the first as and well are advmods attached to it
Not cc: for between two clauses is mark, and so is advmod. Either, neither, both and the not of not only before the first conjunct are preconj. In but also, only but is cc; also is an advmod.

“He stumbled but recovered.”

nsubj Nominal subject
ROOT Root of the sentence
cc Coordinating conjunction
conj Conjunct

Coordinated verbs — 'but' and 'recovered' both attach to 'stumbled', the root

“We waited, but nobody came.”

nsubj Nominal subject
ROOT Root of the sentence
cc Coordinating conjunction
conj Conjunct

Two clauses — 'but' attaches to 'waited', and 'came' is the conj of 'waited'

“She bought bread as well as milk.”

Three words, one conjunction: the last 'as' is the cc, and 'as' and 'well' attach to it

“Two plus two is four.”

In a sum, 'plus' joins two numbers like 'and': it is the cc, and the second 'two' is the conj

conj Conjunct

Every conjunct after the first. The joined parts can be nouns, verbs, adjectives or whole clauses, and the label is always conj.

How the parser decides: the word is coordinated with an earlier one of the same kind. Its head is the first conjunct in a two-part coordination, or the previous conjunct in a longer chain.

“The room was cold and damp.”

det Determiner
nsubj Nominal subject
ROOT Root of the sentence
acomp Adjectival complement
cc Coordinating conjunction
conj Conjunct

Joining adjectives — 'cold' is the acomp, and 'damp' attaches to 'cold'

“The lights dimmed and the crowd hushed.”

Joining whole clauses — 'hushed' has its own subject but still attaches to 'dimmed'

With three or more conjuncts, the relation forms a chain. Each later conjunct attaches to the one just before it, and so does the conjunction. They do not all attach to the first. This changes the head you click in the Dependencies exercise.

“She cooked, cleaned and organised.”

A three-way chain — 'cleaned' attaches to 'cooked'; 'and' and 'organised' attach to 'cleaned'

preconj Pre-correlative conjunction

The first half of a correlative pair: the either of either…or, the neither of neither…nor, the both of both…and, the not of not only…but also. It is rare, but the practice sentence at the end of this page has one.

How the parser decides: a conjunction-like word before the first conjunct, not between the conjuncts. Like cc, it attaches to the first conjunct. The conjunction in the middle is still a plain cc. With no second half, both and either are determiners (det): both cats, either road.

Every word that takes preconj

either, neither, both, and the not of not only. The only attaches to not as an advmod.
Not preconj: the same words with no second half are det. The whether of whether…or not opens a clause, so it is a mark.

“Either Ana or Luis will drive.”

preconj Pre-correlative conjunction
nsubj Nominal subject
cc Coordinating conjunction
conj Conjunct
aux Auxiliary
ROOT Root of the sentence

'Either' is the preconj; 'or' is still an ordinary cc

“Both the cat and the dog escaped.”

The same shape with 'both…and', this time joining two noun phrases

“She plays not only the piano but also the violin.”

'not' is the preconj, with 'only' attached to it; 'but' is the cc, and 'also' attaches to 'but'

Quick check

In Priya bought a lamp and a rug, what is the head of rug, and where does and attach?
Answer
Both attach to lamp, the first conjunct: rug as its conj, and as its cc. Only lamp takes the group’s role: it is the dobj of bought. Neither rug nor and attaches to bought.
In The flag is yellow, blue and red, what is the head of red? What is the head of and?
Answer
The head of each is blue. In a list of three or more, each conjunct attaches to the one just before it (blue to yellow, red to blue), and so does the conjunction. Only the first conjunct, yellow, attaches to the verb: it is the acomp of is.
Which Both is a preconj, and what is its head? Both buses were late. Both the bus and the train were late.
Answer
The second. There, Both is the first half of both…and, so it is the preconj of bus, the first conjunct. In the first sentence there is no second half, so Both is a determiner: the det of buses.
Which word is a cc and which is a mark? The library closed early because the power failed. The library closed early, but the bakery stayed open.
Answer
The mark is because, and the cc is but. Move each conjunction and its clause to the front. Because the power failed, the library closed early works. But the bakery stayed open, the library closed early is not possible. So because makes its clause depend on the other one, and but joins two equals. In the tree, because attaches to failed and but attaches to closed.

Key terms

Conjunct: One of the things being joined. The first conjunct is the head of the whole coordination; each later one is labelled conj. Carlos and Rosa danced. — Rosa is the conj of Carlos. She washed and dried the plates.
Coordinating conjunction: A word joining equals, such as and, but, or, nor or yet. Labelled cc, and attached to the conjunct before it. The hotel was small but clean. We waited, but nobody came.
See: Imperatives & Conjunctions
Correlative pair: A two-part conjunction: either…or, neither…nor or both…and. The leading half is preconj; the middle half stays cc. Either Diego or Marta will cook. Both my aunt and my uncle called.
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.
See: Imperatives & Conjunctions · Tense

Practice on a real sentence

This sentence has all three relations. Its two conjuncts are verbs, so the first conjunct, knows, is also the root. The preconj, the cc and the conj all attach to it. Then look at queen. It is what she knows and also what she corresponds with, but in a tree every word has only one head. Which head does it get? The same sentence is drawn in both views on Dependency Parsing.

Loading the practice sentence…