Conjunction

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Definitions

Authorities do not fully agree about a number of areas of English grammar. Conjunction is one of those. What follows is, therefore, debatable in places but with the intention of providing working definitions to help language teachers analyse, explain and plan.

Conjunction vs. Conjunct

Consider these four, focusing on the bits in black.

I was very late but managed to catch up.
I came late. However, I managed to catch up
or
I managed, however, to catch up.
I went home because I felt unwell.
I felt unwell. Consequently, I went home.

What happens if you remove the bits in black? Click here when you have an answer.

I was very late but managed to catch up.
If you remove the bit in black here, you get an ungrammatical sentence (called a run-on sentence, by the way) so you have to split it into two and re-insert the subject, I, as, e.g.:
I was very late. I managed to catch up
You also lose some of the sense.
I came late. However, I managed to catch up. or I managed, however, to catch up.
In this, removing the bit in black does not produce anything ungrammatical although some sense is lost.
I went home because I felt unwell.
If you remove the bit in black, you get an ungrammatical sentence (another run-on sentence). You also lose the sense of the reason.
I felt unwell. Consequently, I went home.
Removing the bit in black leaves two perfectly grammatical sentence but, again, you lose the sense of the reason.

All the sentences exemplify a form of conjunction but there is a difference:

Sentences 1 and 3 contain conjunctions.
Sentences 2 and 4 express similar concepts but they contain conjuncts, not conjunctions.

The test is: are the expressions an integral part of the clause or not?
If they are, you are dealing with conjunctions, if they are not, you are dealing with conjuncts.
That's a working definition and applies to the sorts of conjunctions called subordinators (the most numerous class). It does not fully apply to coordinators, as we shall see. For a proper guide to the differences between coordination and subordination, see the separate guide. That will open in a new tab and it is also linked in the list at the end.

Two important points

A conjunction proper is integral to the syntax of the sentence. Removing it makes nonsense.
Conjunctions do not normally occur together so we do not have sentences such as
    *She came with Mary and but they were late
or
    *As much as before I left I enjoyed the play
Conjuncts, on the other hand, often occur with other conjuncts and also occur in combination with conjunctions so we can have, e.g.:
    I wanted to talk to the boss but, obviously, she was too busy to see me
    In my view, they play was good although, however, obviously under-rehearsed

Types of conjunctions

There are 3 sorts of conjunction in this list of six. Can you separate them into three classes, two of each? Click here when you have.

whether ... or
but
because
if
not only ... but (also)
so

Coordinating conjunctions	Subordinating conjunctions	Correlative conjunctions
but so	because if	whether ... or not only ... but (also)

We can take these one at a time.

Coordinating conjunctions

These function to join two clauses of equal weight or value. Some coordinating conjunctions can join two words, two phrases or two clauses. They can all be used to join two clauses. There are, in fact, only seven of them in modern English and four of them are quite formal and rare.
They are: and, but, yet, for, so that, nor and or.
Think for a moment about what these do and then click here for the answer.

and: is the simplest and first learned. It's often a simple additive, joining words, phrases or clauses. For example:
    That's all well and good
    John made lunch and Peter ate it
    I ate cheese and ham
    I paid for the entrance fees and the lunch tickets
It has other functions, too, replacing conditional conjunctions, showing chronological ordering and consequence among them. For example:
    Give me a lift home and I'll buy you a drink (conditional)
    I fixed the car and put away the tools carefully (ordering)
    She lost her money and had to walk home (consequence)
but: works in the same way but is (usually) adversative or contrastive. The word also joins single words, phrases or clauses. E.g.:
    It's naughty but nice
    John cooked lunch but Peter ate it
    He came in the morning but not in the afternoon
yet: is similar to but in meaning and is adversative. It can be used to join words or phrases rather than clauses but that is somewhat unusual. E.g.:
He wants to be an engineer yet he speaks no English
She was exhausted yet happy with the work
for: offers a reason for something. This one cannot be used to join items smaller than a clause. E.g.:
He is studying mathematics for he wants to be an engineer
so that: this conjunction has two meanings. When it is a coordinator it refers to the result of the main clause as in, e.g.
The clouds were very dark so that I thought it would rain
Its much more common use is as a subordinator and then it refers to the purpose of the main clause as in e.g.:
I took the car to the workshop so that he could look at it
nor: reiterates a negative when it occurs without neither. E.g.:
    I don't want to go nor do I want to hear about it
Nor requires inversion (i.e., a question form) in English and the negative is carried over from the first clause. It is unusual for this one to be used to join anything less than two clauses even if the second is a simple verb phrase. It can, however, join two smaller units but the result is somewhat formal, as in, for example:
    I didn't find it in the fridge nor the cupboard
    It wasn't comfortable nor cheap
The correlation using neither ... nor is more commonly used to express this concept.
See the notes under correlating conjunctions for more.
or: this also occurs without its partner either and serves to exclude something. E.g.:
She will write to him or she will telephone him
In English, unless the speaker specifically signals otherwise, the conjunction is exclusive so the example above cannot imply that she will both write and telephone. That is not the case in all languages.
It also joins words, phrases or clauses:
You can the red one or the white one
You can sit at the front or at the side

The grammar

These conjunctions must come between the two joined items. Putting them anywhere else results in nonsense:
    *Or you can sit here over there
    *And the man the woman
    *I called he was out but
etc.
Parts of the second item are often ellipted in sentences with or and nor, e.g.:
I don't want to go nor hear about it
She will write to him or telephone
The conjunction and is conventionally ellipted (or replaced by commas) in lists of more than two items (words, phrases and clauses). This is called asyndetic coordination (a term your learners don't need) and also occurs for stylistic effect between adverbs and adjective as in, e.g.
    Slowly, cautiously he climbed the ridge
    Happy, relaxed at last, he went to bed.
Syndetic coordination, on the other hand would have:
    Happy and relaxed at last, he went to bed

Coordination of clauses is not as simple as the list above implies. For more, see the guide to clausal coordination, linked in the list of related guides at the end.

Correlative conjunctions

These conjunctions serve to bind ideas closely together. In that sense many of them function as coordinators and are, in fact, often seen as a subset of those. They are, in fact, not all coordinating conjunctions but many are. The ones that are coordinators join two clauses or other items of equal weight and value.
Others, such as no sooner ... when are purely subordinators
Here's a list of some of the most common ones:

Conjunction	Notes	Examples
as ... as	this is commonly, but not exclusively, used in similes, comparing adjectives, usually inserting just before the first as emphasises the degree of similarity This is a coordinator	He's as stupid as he is wilful as sober as a judge
both ... and	the use of both with and is a focusing emphasiser The phrase is a coordinator.	Both she and John avoided the subject
hardly ... when / than	grammatically, these require inversion if they are fronted because their sense is negative for the same reason, they can't be negated so you can't have, e.g., No sooner didn't they ... if they are fronted, the second element is normally when* but in other positions, than is more frequent these are subordinators	Hardly / Scarcely / No sooner / Barely had I sat down when the phone rang I had hardly / scarcely / no sooner / barely sat down than the phone rang
scarcely ... when / than
no sooner ... when / than
barely ... when / than
either ... or	denotes exclusion of one possibility and is a coordinator	Either you do it or I will
neither ... nor	denotes that both possibilities are excluded and is a coordinator	I will neither enjoy it nor understand it
if ... then	this emphasises the conditionality of the if structure it can be further emphasised with only then then can only* be used if the* if-clause comes first this is a subordinator	If the weather is fine (then) I will come
whether ... or	this usually sets up a clause which is evaluated as if it were a noun as the subject of a verb it also frequently follows an it-phrase it is a coordinator	Whether you do it or I do it doesn't matter It doesn't matter whether you come or not
not only ... but also	this functions much like and but is a much more emphatic way to link two clauses, words or phrases because it carries a negative sense, it requires the inversion if not only is fronted it is a coordinator	Not only did he arrive but he was (also) early He not only arrived but he was (also) early
rather ... than sooner ... than	these are quite rare and often link two nouns or two adjectives often in fixed or semi-fixed binomials They can also link two clauses they are subordinators	Rather dead than red Rather you than me I'd sooner / rather stay at home than go out in this weather

The grammar

It is worth noting that some of these correlatives are actually rather complex. In particular:

The issue of inversion with some of them requires attention.
1. Inversion occurs conventionally with hardly, scarcely, no sooner, barely and not only so we have, e.g.:
  Hardly / Scarcely / No sooner / Barely had I arrived when the phone rang
  Not only does he want too much money, he wants it now
2. With neither ... nor the inversion occurs with full clauses only in the second element:
  She neither wants to go shopping nor does she want to stay at home
  Even when nor or neither stands alone, the inversion still occurs:
  She doesn't want to go shopping, neither / nor does she want to stay at home.
  See point d., below.
The clause-order constraint with the if ... then construction is important because then can only be inserted in the second clause. We allow, therefore:
    If I have time then I will come
    I will come if I have time
    If I have time I will come
but not:
    *Then I will come if I have time
Verb concord is sometimes an issue. The neither ... nor and either ... or structures conventionally require a singular verb but this is often ignored. Compare, e.g.:
    Either John or Mary does the cooking
    Either John or the children do (?does) the cooking
    Neither John nor Mary usually comes (?come) early
    Neither the men nor the women is (?are) waiting
The rule of thumb is that the verb will agree with the second element. So we get:
    Either the children or the parent needs to be present
vs.
    Either the parent or the children need to be present
This can lead to very awkward expressions such as:
    Neither John nor I am (?is, ?are) coming
which are best avoided by rephrasing.
The choice of or or nor after a negative clauses causes some stylistic problems. It is acceptable, for example to have:
    She didn't want to come to the theatre, nor did she fancy going to a restaurant
and
    She didn't want to come to the theatre or fancy going to a restaurant
and both of those can be rephrased with the full correlating conjunctions as:
    She didn't either want to come to the theatre or fancy going to a restaurant
or
    She neither wanted to come to the theatre nor fancied going to a restaurant
With neither ... nor we need to repeat the past-tense form of the verb because it cannot be assumed from the form of the verb in the first clause. With either ... or, we can assume that the negative operator didn't applies to both verbs.
However, it is usually considered wrong to have:
    *She didn't want to come to the theatre nor fancy going to a restaurant
where the use of nor is considered mistaken or at least stylistically clumsy.
The rules are:
1. When the second item is a verb phrase, a noun phrase, an adverb phrase or an adjective phrase then use or, not nor, so we get:
      She hasn’t eaten or drunk anything
      He didn’t study French or German at school
      She never went happily or quickly
      The pie wasn’t well cooked or hot enough
2. When the second item is a full clause, negation needs to be reiterated because it cannot safely be assumed to carry on from the first clause, use nor, not or:
      The teacher didn’t notice the error, nor did anyone else correct it.
      My students weren’t late to class and nor were most of their colleagues
      She didn’t come happily to the theatre, nor did she enjoy the play when she got there
  and here, too, we have the inversion of operator and verb in the second clause. Clearly, if a new subject is used for the second verb a new clause rather than verb phrase is inevitable so nor is the only option.
The position of the optional also in not only but (also) construction causes problems. With this construction, the two parts need to be in the same syntactical position. We can have, therefore:
    We have not only the money but (also) the time
with both items preceding the object noun phrases
    She not only broke her leg in two places but also cut her head badly
with both items preceding the verb phrases
Compare the clumsy (if not wrong):
    ?We not only have the money but also the time
    ?She broke not only her leg in two places but also cut her head badly

Subordinating conjunctions

There is a separate guide to clausal subordination, linked in the list below, which covers some of the following but takes a slightly different approach to categorisation.

There are many subordinating conjunction and they are more complex in both structure and meaning. They join clauses.

They differ from coordinating conjunctions in that they are not used to join clauses of equal value but to indicate that one clause is subordinate to or dependent for its meaning on the other (hence the name).
If you would like to know more about Matrix and Subordinating clauses, go to the guide to clause structure (new tab).

Here's the list:

Type	Conjunctions		Examples
Concession indicate that the speaker/writer is conceding a point	*though although even though while †that †as		Although / even though / though it's raining, I'll take a walk While I understand your point, I still disagree
Comparison / Contrast compare items or clauses and contrast ideas	than rather ... than whether like as much as whereas while whilst		She is younger than I am I would rather go than stay I don't know whether he's serious or trying to be funny They talked to me like I was a stupid child As much as she loves him, she won't stay I prefer to stay at home while she prefers eating out I had eaten whereas they went hungry
Time indicate the relationship in time of two clauses, one determined by the other	after as long as as soon as before by the time now that once	as since till until when whenever while	She came after the party had finished They stayed as long as it lasted I showered before I had lunch I will have finished by the time you arrive I have lived here since I was a child Whenever I ask him, he avoids the subject
Reason indicate the causal connections between acts or states	because since so that in order (that) in order to (often contracted to 'to') why for lest for fear that		I left because he arrived I'll tell you, since you ask He nailed it down so that it wouldn't move This is the reason why I dislike it I didn't argue for I saw she was getting angry I took an umbrella lest it rain She left early for fear that she would miss her train
Manner show behavioural links between clauses	how as though as if like		I did it how I was told to do it He speaks as though / if he is the boss She spoke like she meant it
Place show locational links	where wherever		I will stay where / wherever I like
Condition show how one clause depends on the fulfilment of another	if only if whether unless provided / providing (that) supposing (that) assuming (that) even if in case (that)		If it's raining we'll go home Only if you promise will I accept I won't go unless I'm invited Supposing he declines, what will you say? Even if he does say no, I'll go ahead She brought her car in case there were no taxis around I don't know whether I dare ask

* The conjunction though may be used non-initially as in, e.g.:
Rich though he was, he never gave anything away
This kind of ordering marks the adjective for emphasis.

† The words that and as can act concessively in very formal and unusual expressions such as:
    He never gave anything away, rich that he was
    Late as I was, I didn't miss most of the introduction
which is more often expressed with although as in:
    He never gave anything away although he was rich
    I didn't miss most of the introduction although I was late
In this case, the conjunctions are also unusual in not taking the initial position in the clause.

The grammar

The greatest difference between coordination and subordination is clause ordering:

Coordinating conjunctions
1. fit between clauses only. You can't have:
  *And I had lunch I had tea.
2. with simple additive coordinators, we can often reverse the order of the clauses without damaging the sense.
  I like him and he is my friend
  is the same as
  He is my friend and I like him
  (although speakers front items for a purpose; for more, try the guide to fronting, linked below).
3. with some coordinators, the clause ordering carries the meaning. Compare
  I was bored so I went to the cinema
  with
  I went to the cinema so I was bored.
Subordinating conjunctions
1. allow more leeway in clause ordering and their positions. We can have
  If you see him, say hello for me
  and
  Say hello for me if you see him
  with equivalent meanings (although, again, speakers front items for a purpose).
2. however, reversing the ordering of clauses requires us to move the conjunction which is attached to the subordinate clause, too. We can have
      She took a coat because it was raining
  and
      Because it was raining she took a coat
  but
      It was raining because she took a coat
  is not what we mean at all.

There are separate guides to coordination and subordination on this site which go into much more detail and both are linked below. There is also a guide to coordination vs. subordination, linked below.

Some other notes on the subordinating conjunctions:

the concessives all mean pretty much the same thing but while cannot be used if there is a chance of ambiguity so we would not normally encounter
    While it is raining, I'll take a walk
because that might imply something like
    When it is raining
rather than
    Although it is raining
some comparison subordinators also refer to time:
I came as soon as I could
etc.
some words used as time subordinators are prepositions in other environments. E.g., in
I showered before lunch
the word before is a preposition but in:
I showered before Mary came home
the word is a subordinating conjunction.
An alternative way to analyse this is to say that the word is a preposition in both cases but in the second the clause is nominalised (acting as a noun). That is not the line taken here.
The conjunctions since, after, until, till can act similarly. For more, see the guide to prepositions of time, linked below.
there are a number of conjunctions which have an optional that with no change in meaning: now that, considering that, seeing that etc.
ellipsis or substitution of verbs with pro-forms in the second clause is quite common:
She went because I did (go)
Is she being serious or (is she) not (being serious)?
some analyses add in the relative pronouns because they function as conjunctions. This site has a separate guide to relative pronoun clauses, linked below. They are common ways to subordinate.

Summary

Here's a summary of the main types of conjunction. The list of coordinators is complete but the other sections contain examples only of the many conjunctions which operate as subordinators. The conjunction so appears twice because it is a coordinator when it signals a result and a subordinator when it signals a reason.
The first three coordinating conjunctions are considered the core coordinators and the other five have some subordination-like characteristics.
More detail is in the separate guides to coordination and subordination, linked below.
summary

Equivalent conjuncts

The meaning and function of most conjunctions of all types can be expressed using conjuncts (i.e., connectors which lie outside the clause structure). Conjuncts connect full sentences rather than making connections between clauses within sentences.
There is a guide to adverbials, linked below, on this site which includes more consideration of conjuncts an there is a guide to conjuncts only.

So, for example, we can have the same ideas expressed in two ways:

conjunction	conjunct
I asked to see him but he was busy.	I asked to see him. However, he was busy.
He is overbearing and people find him boorish.	He is overbearing. Moreover, people find him boorish.
She was smiling so he believed she was not serious.	She was smiling. He consequently believed she was not serious.

A common error is for learners (and native speakers) to use conjuncts when they need a conjunction and vice versa. As you can see from the examples above, the grammar needs to be adjusted in order to make them even near equivalents. So we get errors, for example:
    *I asked to see him, however he was busy
    *I had lunch moreover it was delicious
    *She was smiling, consequently he believed she was not serious
It is possible to make these sentences work by inserting a semi-colon after the first clause.
Conjuncts are usually more emphatic and, of course, do a great deal else in the language.

Pronunciation issues

Features of connected speech affect how linked or bound clauses are pronounced in the normal way of things so rhythm and stressing are features which need to be taught (not just practised in a parroting way).
However, additionally, all conjunctions are function rather than content lexemes and subject to a good deal of weakening and reduction in rapid connected speech, in particular.

and
is often reduced to /ənd/, /ən/, /nd/ or /n̩/ rather than appearing in its citation form /ænd/ so, for example:
    She came and talked to me
may be pronounced as:
    /ʃi.keɪm.ənd.ˈtɔːkt.tə.miː/
or
    /ʃi.keɪm.ən.ˈtɔːkt.tə.miː/
or
    /ʃi.keɪm.n̩.ˈtɔːkt.tə.miː/.
but
is often reduced to /bət/ or /bə/ rather than appearing in its citation form /bʌt/ so, for example:
    She came but didn't talk to me
may be pronounced as:
    /ʃi.keɪm.bət.ˈdɪdnt.ˈtɔːk.tə.miː/
or
    /ʃi.keɪm.bə.ˈdɪdnt.ˈtɔːk.tə.miː/
if
is often almost inaudible and pronounced as /f/ rather than /ɪf/ so, for example:
    If he's not here soon, we'll start without him
will not usually be pronounced carefully as:
    /ɪf.hiz.nɒt.hɪə.suːn/ /wil.stɑːt.wɪð.ˈaʊt.ɪm/
but as:
    /fiːz.nɒt.hɪə.suːn/ /wil.stɑːt.wɪð.ˈaʊt.ɪm/
and learners, unless they have been alerted to the fact and given some practice at identifying the conjunction in connected speech may miss the conditional nature of the sentence altogether.
because
is often reduced and made monosyllabic as /kɒz/ rather than /bɪˈkɒz/ so, for example:
She came because I asked
may be pronounced as:
/ʃi.keɪm.ˈkɒz.ˈaɪ.ˈɑːskt/
unless
may be reduced to /les/ so:
We'll wait for him unless you need to go
may appear in rapid speech as:
/wil.weɪt.fər.ɪm.ˈles.ju.niːd.tə.ɡəʊ/

Classroom implications

The above may look (and is slightly) all rather theoretical but there are significant implications for teaching.

Think for a moment about what these might be and then click here.

The first obvious one is that these forms and the nature of conjunction vary widely across languages and translation is fraught with difficulty. In some languages, the distinction between conjunct and conjunction is blurred or absent, in others a two-part conjunction is required for ideas represented by because and so and there is a temptation to produce
*Because it was late so I took a taxi
etc.
In some languages, ideas which are expressed through conjunction in English are expressed through extra-clausal conjuncts and vice versa. That will cause significant formal and conceptual difficulty. Errors such as:
*I took an umbrella. Because of it was raining.
*It was raining. So I took an umbrella
result.
English is rich in conjunctions and if we aren't careful, the sheer number and variation can bewilder the learner. We need to analyse carefully, therefore, when deciding what we present and how we present it, breaking the area up into digestible units with similar conceptual characteristics.
Some words, such as since, until, whether and others can appear in more than one guise. They may be conjunctions in one setting and prepositions in another; they may be subordinating conditionals or subordinating comparatives, so we need to be able to analyse accurately or we will give our learners confusing signals or the wrong information. For example:
    Since it was such lovely weather, we went for a walk
in which the word is a subordinating reason conjunction and
    I have been here since the war
in which it is a preposition and
    I have been here since I retired from the army
in which it is a subordinating time conjunction..
Written language relies heavily on precise conjunction use to show relationships and maintain cohesion (in speaking we are often content to use simple coordinating conjunctions). Learners who need to use written English, for example, in their work or studies, will need careful training and lots of practice in this area if they are to avoid mixing conjunct, disjunct and conjunction and making formal errors. For more examples, see the guide to expressing cause and effect in the functions section.
The use of conjunction in both spoken and written language is essential to maintaining fluency, cohesion and coherence so we should be sure to focus on the area at all levels. It is often a subject neglected in course materials.
Communicatively, one can get away with short staccato sentences, neglecting conjunction use altogether, but any level above the most elementary will require good conjunction use. A key element of successful communication is not just the ability to say what will, did and might happen but to say how actions and states are connected and related to each other – that's the job of conjunctions and conjuncts.

Related guides
the word-class map	for links to guides to the other major word classes
coordination vs. subordination	these three guides all consider the role of conjunctions. Start with the first one if the area is new to you.
coordination
subordination
adverbials	for more considerations of adjuncts, conjuncts and disjuncts
conjuncts	for a guide to only this area
fronting	for a guide to this important area
prepositions of time	for the guide
relative pronoun clauses	to see how relative pronouns function as conjunctions
a classified list of conjunctions	for a simple list in PDF format (new tab)

There is, if you can face it, a test on some of this.