Clausal subordination

subordination

Before tackling this guide, you would be wise to consult the guide to subordination and coordination where the differences and similarities between the phenomena of coordination and subordination are analysed.
This guide deals with a number of issues covered in more detail elsewhere such as conditionality and concession. You can track other guides to the area via the section on syntax: clauses and phrases.

You will know if you have followed the guide to subordination and coordination that compound-complex sentences with mixtures of various types of coordination and subordination are not uncommon in English.
In what follows, for the sake of clarity, we will deal with single instances of subordination at a time and will not consider coordination at all.

The subordinators

We can classify subordinators in two ways:

By their structural characteristics – how they are formed and the nature of the surrounding syntax
By what they do – their function in terms of making meaning

structural characteristics

We can divide the structural characteristics into three classes:

Simple subordinators

This is by far the largest class and contains the subordinators that we would consider the essential subordinators in English. They are all single words and many will be familiar to most learners above A1 level.
Here's a list:

after
although
as
because
before
if
however
lest

once
since
till
unless
until
when(ever)
where(ever)
whence

whereas
whereby
whereupon
while
whilst
whither

Some examples:
After he had driven for 4 hours he stopped for coffee
He couldn't leave until the work was done
Before it rains, we should take the dog out
However you want to do the work is fine with me
I told him it was a stupid idea whereupon he became angry
Whereas I have often worked late, Shirley never does
Once we've finished we can go for a drink

Note that whereupon, whereby and whither apart from being slightly archaic, can only come before the second clause for semantic reasons (they introduce chronological ordering of events).

Compound subordinators

These are rarer. Many insist on being followed by that and some can optionally be followed by that. Others are followed by as and some are simply rather irregular.
Here's a list:

Obligatory that	Optional that	Obligatory as	Others	Some examples:
in that so that in order that such that except that	now that providing that provided that supposing that considering that given that assuming that seeing that	as long as as soon as so long as as much as insofar as as far as	sooner than rather than as if as though in case	He did all the work except that he forgot the painting Now that he's at university, we can rent out his room Considering that he's nearly 80 he's very active Insofar as she could she answered all the questions Assuming that it's open I can get it at the corner shop I'd sooner stay in tonight than go to the party Seeing that it's under guarantee, I don't worry about it We can finish today given that we are all working on it

Correlative subordinators

These consist of two parts but are separated by the independent clause. Here's the (short) list of these with their characteristic function.

Conditional	Concessive	Proportional	Alternative	Some examples:
if ... then	although ... yet	as ... so more/less ... than the ... the	whether ... or	If you cook then I'll wash up Although his handwriting is poor yet it can be understood The more people who come the better it will be

Note that although ... yet is archaic and formal. The sense is most often simply expressed with although.
The use of then in conditional expressions is not obligatory.

shared structural characteristics

All subordinators share certain attributes which distinguish them from coordinators and make them teachable together (but not all of them at once, please).

Clause mobility: It is possible to have, for example,
    I came because I was interested
and
    Because I was interested, I came
and
    Unless you work a bit more, you'll fail the examination
and
    You'll fail the examination unless you work a bit more
Although the emphasis is different, both orderings are grammatically acceptable.
You cannot do this with coordinating conjunctions of course or you get nonsense like:
    *But you weren't at home I telephoned
Subordinators travel with their clause; coordinators are independent of either clause and come between them.
Allowing the addition of other conjunctions: Subordinators can themselves be preceded by coordinators in, for example:
He didn't come because it was raining and because he was too tired
You can leave early provided that you have finished but only if the boss says it's OK
Again, coordinators do not allow that.
Non-elision of the subject: Usually, coordinators allow the elision of the subject but subordinators do not so we can have
    John came home and cooked
a coordinated set of two clauses with ellipsis of the second subject
but not
    *I came in order that could see you
or
    *I won't drink if am driving
Inability to join two equal subordinate clauses: In this part, coordinator in green, subordinators in red.; Coordinators can join two subordinate clauses together as in, e.g.:
    Because I wanted to see you I came to the party and stayed for hours
in which the coordinator and joins two equal-value clauses, but we cannot have:
    *She came when you asked in order that you saw her
because only coordinators can link two subordinate clauses together.
Subordinators can, of course, link a further subordinate clause making a complex tree of subordinations so we can have, e.g.:
    She came to the party because she wanted to talk to him and because she enjoys parties if they are not too large and noisy
Here, we have a main clause:
    She came to the party
a subordinate clause:
    because she wanted to talk to him
linked to another equal-value subordinate clause:
    and because she enjoys parties
with its own subordinate conditional clause:
    if they are not too large and noisy.
If that seems complicated to access, try a diagram:

Theoretically, there is no limit to the number of clauses which can be linked in this way.

function and meaning

Functionally, there are at least the following classifications. There are other ways to do this, of course, because people conceptualise things slightly differently. For teaching purposes, the following will do. You will notice that some subordinators can perform more than one function so appear in more than one category. The examples have been deliberately chosen to apply to the less-frequently encountered items.
The categories are slightly different from those in the guide to conjunctions, by the way.

Function	Subordinators	Examples and notes
conditional	if if ... then providing that provided that supposing (that) on condition that unless as / so long as	If we want to get this done then we'll have to start soon. Supposing that John doesn't pay, what will happen then? Unless I am very much mistaken, that's his brother in law. You can do that just as long as nobody gets hurt. See the guide to conditional and concessive subordination for more. The unusual nature of unless is covered there, too.
concessive	although given (that) in that considering (that) assuming (that) presuming (that) insofar as as far as although ... yet	Given that he has no money, I can see no way he will pay you. Insofar as the work needs doing, I suppose I shall have to pay for it. I will ask him presuming we meet, of course. Although she tried her best, yet she failed to pass. As far as his work is concerned, I have no complaints. See the guide to conditional and concessive subordination for more.
causal	because as since so that in order that such that seeing that in case whereby	I came early so that I could help out a bit. He wrote his essay such that the links between its parts were clear. Seeing that he is unharmed, there's no reason to panic. In case you need me, I'll be by the phone. He opened the hatch whereby he could get onto the roof. The conjunction in case operates differently in AmE and BrE: She will take her laptop in case it's needed is differently understood. In British English, this means She will take her laptop and use it if she needs it In American English, this might mean: She will take her laptop only if there's a need for it Whereby is unusual. The conjunctions as, since and because all function as causal subordinators with the same syntax. The conjunction for, in this sense, is a coordinator. Note that in one of its senses, called resultative, the conjunction so that is actually a coordinator akin to so and not a subordinator. For example: The garden was covered in snow so that he could see the footprints clearly In this sentence, so that can be replaced with a true coordinator such as and or so and it cannot shift position so we don't allow: So that he could see the footprints clearly the garden was covered in snow When it is used in a purposive way to mean something like in order that*, it is a subordinator and we can shift the clauses around as in, e.g.: He fixed it firmly in place so that it wouldn't move So that it wouldn't move he fixed it firmly in place
temporal	after before now that once since till until when(ever) whereupon while whilst as soon as	Now that we have finished the work, we can relax. Once we have finished the work we can relax. I voiced my objection at the meeting whereupon I was fired. Whenever I speak to him, he seems distracted and busy. I cooked whilst my sister did the gardening. Note that since can also act as a preposition as in, e.g., since the war, since 1959 etc. The word whereupon is rare.
exclusive	lest except (that) sooner than rather than whether ... or	I would sooner eat on the terrace than be in this smoky restaurant. He reinforced the floor lest the snooker table be too heavy. Whether he comes or doesn't come, it makes no difference to us. Because of their nature, subordinate clauses in these cases are often severely elided as in, e.g., It makes no difference whether he comes or no(t). The subordinator lest is somewhat old fashioned and is generally followed by a clause in the subjunctive (as in the example).
spatial	where(ever) whence whither	Wherever she looked, she saw enemies. The pub is over the hill, whither we are going today. He knew the city, whence he came, really well. Whence and whither are unusual in modern English and probably not worth troubling any but the most advanced learners with.
comparative / contrastive	as if as though while whilst whereas	He used the stone as though / if it were a hammer. She prefers to eat out while / whilst I prefer eating at home I had eaten whereas the others went hungry Note that both as if and as though are often followed by a subjunctive form. There is a guide this and other uses of the subjunctive on the site. The subordinators while and whilst are also temporal conjunctions.
proportional	as ... so more/less ... than the ... the	The more they shouted the calmer he became. As the evening wore on so they became noisier and more excited. She was more embarrassed than she ever remembered being. In the last example, it is easily argued that the first element of the subordinator is simply a modifier. That is so.

Alternative ways to subordinate

There are 3 major ways in which English can signal a subordination of one clause to another without using a conjunction (although conjunctions are by far the most frequent).

Wh-words and that: Most frequently, wh- words occur in subordinate pronoun and adverb relative clauses. They function to split the main clause, inserting the relative clause into the sentence like this:
    The shop, where you bought the coat, has closed.
The subordination occurs with both defining and non-defining relative clauses:
    The people who came to the party were genuinely friendly.
The relative pronoun that is used in a similar way:
    The dog that bit him belongs to the neighbours.
When omitting the relative pronoun is allowed (i.e., when it stands as the object in a defining clause [see the guide to relative pronoun clauses for more]), subordination still occurs
    The man we asked was very helpful.
There is a guide to relative pronoun clauses on this site (linked below).
Inversions: This is a fairly rare occurrence in English in conditional sentences but in formal writing may be encountered. The usual items are had, were and the putative should:
    Had I known you were coming, I would have got in some beer.
    Were you to try a bit harder, I feel sure you'd understand.
    Should you find yourself in any trouble, call me at once.
Non-finite forms: This is a large category. If you have followed the guide to clause structure, you'll know that independent clauses cannot be non-finite but that a non-finite clause is almost always a marker of subordination. If the terms confuse you, there is a guide to finite and non-finite clauses on this site (linked below). Here are two examples:
    I came to help (non-finite infinitive with to)
    Opening the door, he saw the fire had burnt out (non-finite -ing clause)
These sorts of subordination may be replaced by the use of a subordinator.
    I came so that I can help
    When he opened the door, he saw the fire had burnt out

Related guides
subordination and coordination	for an overview of the area
coordination	for the guide dedicated to this area
syntax: clauses and phrases	for the index to allied areas
conjunctions	for more on the word class in general
so and such	for a short guide to these two troublesome words
conditional and concessive clauses	for more on two specific types of subordination
subjunctive	for more on the other uses of the subjunctive in English
relative pronoun clauses	for more on a particular type of subordination using pronoun forms rather than conjunction
finite and non-finite clauses	for a guide to these two basic clause and verb types
lesson on subordination	a lesson on subordination for higher-level learners
exercise on subordination	a short exercise on subordination to test learners (and you)

Try a short test.