Subordinating Conjunctions

Roger Fielding Published 18 July 2026 · 7 min read Young Learners

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Have you ever written a sentence like this in an essay?

I didn't finish my homework, I was playing games.

Your teacher circles it in red and scribbles something like "run-on sentence" or "comma splice" in the margin. You stare at it and think, "But that's how I'd say it!"

Here's the thing. Your instinct is right that those ideas belong together. What you're missing is the little word that shows how they belong together.

That's where subordinating conjunctions come in — words like because, although, when, if. They connect one idea to another and show the relationship: time, reason, contrast, condition. Once you're comfortable with them, your writing stops sounding like a list of simple sentences and starts flowing like proper, confident English.

Before you read on, here's where we're heading. By the end you'll be able to: - Spot subordinating conjunctions and the dependent clauses they introduce. - Use because, although, when, if — and know their close relatives — to show time, reason, contrast, and condition. - Order your clauses and punctuate them correctly, including commas. - Fix "comma splice" mistakes by using subordination instead of jamming two sentences together.

Beginner (Foundation): What Are Subordinating Conjunctions?

Let's start with the idea of a clause. A clause is a group of words with a verb — something happening now, in the past, or in the future.

I was late.
The bell rang.
We will win.

Some clauses can stand alone as full sentences. These are called independent clauses. Others feel "unfinished" on their own — they need another clause to make sense. Those are dependent clauses.

Compare these:

I was late. ✅ (independent — feels complete)
Because I was late… ❌ (dependent — feels like something's missing)

That feeling of "something's missing" is your clue that you've got a dependent clause. And the word doing that job is usually a subordinating conjunction.

A subordinating conjunction:

Introduces a dependent clause, and
Shows the relationship between that clause and a main clause.

We'll focus on four very common ones, plus a few of their relatives:

because (also since, as) — gives a reason
although (also though, even though) — shows a contrast / concession
when (also while, before, after, as soon as, until) — shows time
if (also unless, provided that) — shows a condition

Here are some simple pairs:

We went inside because it was raining. (Reason: why did we go inside?)
I answered the question although I wasn't sure. (Contrast: this was surprising, because I wasn't sure.)
We lined up when the bell rang. (Time: at what moment did we line up?)
You can go out if you finish your homework. (Condition: only in this situation.)

Notice that in all those examples, the dependent clause can't really stand on its own:

Because it was raining. → feels unfinished
Although I wasn't sure. → unfinished
When the bell rang. → unfinished
If you finish your homework. → unfinished

They need a main clause to lean on.

Common Mistake: Writing the dependent clause as if it were a complete sentence: - Because it was raining. ❌ Instead: We went inside because it was raining. ✅

Quick recap: - A clause has a verb; some can stand alone, some can't. - Independent clauses feel complete on their own. - Dependent clauses don't; they need a main clause. - Subordinating conjunctions (because, although, when, if — and relatives like since, though, while, unless) introduce dependent clauses. - Each one shows a relationship: reason, contrast, time, or condition.

Intermediate (Development): Clause Types, Clause Order and Commas

Once you know what because, although, when, and if do, it helps to see the wider families they belong to — and then get the punctuation locked down.

The main jobs these clauses do

These clauses are called adverbial clauses because, like adverbs, they tell you more about the action in the main clause. There are five families worth knowing:

Reason — because, since, as: We stayed in because it was raining.
Concession/contrast — although, though, even though: Although the exam was hard, she finished early.
Time — when, while, before, after, as soon as, until: We lined up as soon as the bell rang.
Condition — if, unless, provided that: You won't understand unless you listen.
Comparison — than, as…as: She ran faster than I did. This one is closely related but gets its own fuller treatment elsewhere in the library, since it often involves shortened clauses.

Knowing the family helps you choose the right word instead of reaching for "because" every time you mean something slightly different.

1. When the dependent clause comes second

If your sentence starts with the main (independent) clause and the dependent clause comes after, you usually don't need a comma.

We went inside because it was raining.
I answered the question although I wasn't sure.
We lined up when the bell rang.
You can go out if you finish your homework.

You can read these in one smooth breath.

2. When the dependent clause comes first

If your sentence starts with the dependent clause, you usually do need a comma between the clauses.

Because it was raining, we went inside.
Although I wasn't sure, I answered the question.
When the bell rang, we lined up.
If you finish your homework, you can go out.

That comma is a reader-friendly pause. It tells the reader: right, that's the end of the "extra information" bit — here comes the main point.

Pro-Tip: Read your sentence aloud. If you naturally pause between the two parts, you probably need a comma there.

3. Avoiding the "comma splice"

A very common mistake is sticking two complete sentences together with just a comma and no joining word. This is called a comma splice.

I was tired, I went to bed. ❌ (two independent clauses joined only by a comma)

You can fix this in three main ways:

Use a full stop [US: period]: I was tired. I went to bed. ✅
Use a co-ordinating conjunction (see Article H7.1): I was tired, so I went to bed. ✅
Use a subordinating conjunction to make one clause dependent: Because I was tired, I went to bed. ✅ or I went to bed because I was tired. ✅

That last option is what we're practising here — turning one idea into a dependent clause with because, although, when, if (or a relative like since, though, unless).

Common Mistake: - It was late, we went home. ❌ (comma splice) Better: Because it was late, we went home. ✅ or It was late, so we went home. ✅

Quick recap: - Subordinating conjunctions fall into families: reason, contrast, time, condition, comparison. - Main clause first → usually no comma: We stayed in because it rained. - Dependent clause first → usually a comma: Because it rained, we stayed in. - A comma splice is two complete sentences joined only by a comma. - Fix a comma splice by using because, although, when, if (or a relative) to make one clause dependent.

Advanced (Mastery): Nuance, Exceptions and Style

If you're comfortable spotting and punctuating basic sentences with because, although, when, if, you're ready to look deeper at how skilled writers actually use these words — including where the "rules" get less tidy.

1. Watch the multi-duty words

Some conjunctions do more than one job, and you have to use context to work out which:

Since can mean because (reason) or from that time (time): Since you're free, help with the posters (reason) vs I've been nervous since the results came out (time).
While can mean during the time that (time) or whereas/although (contrast): While I was waiting, I read a chapter (time) vs While maths is her strength, English takes more work (contrast).
As can signal time, reason, or manner, which is exactly why stacking several as-clauses in one paragraph can blur meaning. If precision matters — an exam essay under time pressure, say — swap in because or when so the reader isn't left guessing.

2. Clause order changes emphasis, not meaning

Swapping the order of the clauses rarely changes the basic facts, but it does shift what gets the spotlight.

Because I was ill, I stayed in. (Emphasis on the reason.)
I stayed in because I was ill. (Emphasis on what I did.)

Writers use this deliberately for effect:

When the whistle blew, the crowd roared. (dramatic build-up)
The crowd roared when the whistle blew. (more neutral)

In your own stories or essays, think about which part deserves to land first.

3. Fragments — a stylistic choice, not always an error

Strictly, a dependent clause standing alone is a sentence fragment:

If you tell anyone. ❌ (as a formal sentence)
When you're ready. ❌ (as a formal sentence)

In an exam answer or a formal essay, these would usually be marked wrong. But in fiction and dialogue, they can create drama or mimic real speech — a character trailing off, a line of tension. The skill is knowing which register you're in.

Pro-Tip: For exams and formal homework, use complete sentences with clear subordination. Save fragments like "If you say so." for dialogue or deliberate creative effect.

4. Don't confuse with relative clauses

Subordinating conjunctions introduce adverbial clauses. Words like who, which, that, where introduce relative clauses, which do a different job entirely: they describe a noun rather than giving a reason, time, or condition.

The boy who was late missed the bus. (relative clause — tells us which boy)
The boy missed the bus because he was late. (adverbial clause — tells us why he missed it)

If you're unsure which you're looking at, ask: "Is this bit telling me more about a noun, or about the whole action?" For the full picture on relative clauses, see Article H2.5.

Quick recap: - Since, while, and as can each mean more than one thing — use context, or swap in a clearer word. - Reordering clauses changes emphasis, not the underlying facts. - Dependent-clause fragments are fine in fiction and speech, risky in formal writing. - Adverbial clauses (why/when/if) are different from relative clauses (which describe a noun).

UK vs US note: I'm using UK spelling here (for example, colour [US: color]) and the UK term full stop [US: period]. The grammar of subordinating conjunctions — the words themselves, the clause order, the comma rule — is identical in UK and US English. Only spelling and a few terms differ.

Key Takeaways

Subordinating conjunctions like because, although, when, if (and relatives like since, though, while, unless) introduce dependent (adverbial) clauses.
These clauses can't stand alone; they need a main clause.
Dependent clause first → comma. Dependent clause second → usually no comma.
A comma splice is two complete sentences joined only by a comma — fix it with subordination.
Different conjunctions show different relationships: reason, contrast, time, condition, comparison — and clause order shifts emphasis.

Check Your Understanding

Underline the dependent clause and circle the subordinating conjunction: We stayed at school because it was raining heavily.
Add a subordinating conjunction (because, although, when, if): ___ it stopped snowing, we went outside to play.
Rewrite this comma splice using a subordinating conjunction: It was very noisy, I couldn't concentrate.
Add a comma if one is needed: If you see Mia tell her I called.
Is the bold clause adverbial or relative? The teacher smiled when she saw our marks.

Answer Key

Dependent clause: because it was raining heavily; conjunction: because.
When it stopped snowing, we went outside to play.
Because it was very noisy, I couldn't concentrate. (or: I couldn't concentrate because it was very noisy.)
If you see Mia, tell her I called. (comma needed — dependent clause comes first)
Adverbial (time — when did she smile?)

Internal Links

H0 — What Is Grammar, Really? (foundational overview)
H7.1 — Co-ordinating Conjunctions: And, But, Or, So (joining equal ideas, not dependent ones)
H7.4 — Conjunctions of Time, Cause, and Contrast (a wider toolkit beyond our four)
H2.5 — Relative Clauses: Who, Which, That (clauses that describe nouns, not actions)
Forward — the Clauses pillar (coming soon), for the full picture of independent and dependent clauses