Subordinating conjunctions introduce dependent clauses — clauses that cannot stand alone as complete sentences. Words like 'because', 'although', 'when', 'if', and 'unless' are among the most frequently used conjunctions in English, and students begin encountering them at very early levels. However, two serious errors persist even among intermediate learners: writing a dependent clause as if it were a complete sentence ('Because she was sick.'), and pairing a subordinating conjunction with a coordinating conjunction in the same sentence ('Although she tried hard, but she failed.'). This lesson builds the foundational knowledge to prevent both. Note: this lesson introduces subordinating conjunctions as a class; adverb clauses — where these conjunctions most commonly appear — are covered in depth in Lesson 7 of the adverbs series.
Before you start — think honestly about your own teaching and experience.
Look at the examples. Answer each question before reading the explanation — this is how your students will learn too.
The second version uses the same words as the first but adds 'because'. Why does that make it incomplete? What does 'because' do to the clause it introduces? What is missing from the second version that the third version provides?
'Because' is a subordinating conjunction — it signals that the clause it introduces is dependent on another clause for its meaning. On its own, 'Because the students were tired' raises an expectation: because of this, what happened? The reader is left waiting for the main clause. This is why it cannot stand alone as a sentence. Adding the main clause ('The teacher stopped early') completes the meaning. This is the fundamental principle behind all subordinating conjunctions: they create dependency, not completion.
Although the classroom was dark, but the students kept working. ✗
Why is the third sentence wrong? What job is 'although' already doing that makes 'but' unnecessary? What is this error called?
'Although' is a subordinating conjunction that already signals contrast between the two clauses. 'But' is a coordinating conjunction that also signals contrast. Using both in the same sentence to express the same relationship is called a conjunction collision — both conjunctions are doing the same job twice. The sentence needs one or the other, not both. This error (also 'because...so', 'even though...but') is extremely common at B1 level and worth addressing directly. See also Lesson 7 of the adverbs series for the full treatment of adverb clauses introduced by these conjunctions.
Are 'when' and 'if' interchangeable in these sentences? What does 'when' assume about the event? What does 'if' assume?
'When' assumes the event will definitely happen — the speaker is certain they will finish school today. 'If' introduces a condition — it is possible but not certain that they will finish early. Students whose first language uses the same word for both often confuse them. 'When I win the lottery, I will buy a new school' sounds wrong to a native English speaker because winning the lottery is uncertain — 'if' is needed. The key question: is the event certain or merely possible?
| Form | Use / Meaning | Example |
|---|---|---|
| Type | Conjunctions | Key distinction |
| Time | when, before, after, while, until, as soon as | 'When' = certain event; use 'if' for uncertain events |
| Cause | because, since, as | 'Because' = direct cause; 'since/as' = known background reason |
| Contrast | although, even though, while, whereas | 'Although' = simple contrast; 'even though' = stronger surprise |
| Condition | if, unless, as long as, provided that | 'If' = possible; 'unless' = 'if not' (no second negative needed) |
| Purpose | so that, in order that | Expresses deliberate goal — not the same as 'so' (result) |
The difference between 'because', 'since', and 'as' is worth knowing even though all three express cause. 'Because' gives a direct, specific reason and answers the question 'why?'. It is the most neutral and most common choice. 'Since' introduces a reason the listener already knows or can be assumed to know: 'Since it was the last day of term, the teacher allowed the students to choose their activity' — both speaker and listener understand the context. 'As' is similar to 'since' in formal writing: 'As the school had no water, lessons were suspended.' In everyday speech, 'because' is almost always the safest choice. Note also that 'since' has a separate time meaning ('since 2018') — see Lesson 3 of the adverbs series for the tense rules that apply when 'since' is used as a time expression rather than a cause conjunction.
Quick checks: • Is there a subordinating conjunction with no main clause? → Fragment — add a main clause • Does the sentence have both 'although' and 'but' (or 'because' and 'so')? → Conjunction collision — remove one • Does the dependent clause come first? → Add a comma after it • Is the event certain or hypothetical? → Certain = 'when'; hypothetical = 'if' • Does the sentence use 'unless'? → The main clause should be positive — 'unless' already contains the negative
Choose the correct subordinating conjunction for each sentence.
Each sentence contains one error related to subordinating conjunctions. Find and correct it.
Use this sequence directly in class — guided discovery, no textbook needed. Tap each step to mark it done.
STEP 1 — Complete or incomplete? (5 min): Read out five clause starters, some complete sentences and some fragments beginning with a subordinating conjunction. Students call 'complete' or 'incomplete'. For each incomplete one, ask a student to add a main clause to complete it. This immediately establishes what a dependent clause is.
STEP 2 — What relationship? (5 min): Write five subordinating conjunctions on the board: because, although, when, if, unless. Ask students to tell you what each one signals (cause, contrast, time, condition, condition-negative). Build a simple table on the board. Ask students to give one example of each from their own classroom experience.
STEP 3 — Collision clinic (5 min): Write three collision sentences on the board: 'Although...but', 'Because...so', 'Even though...but'. Ask students to identify the error and give two correct alternatives for each. Emphasise: one relationship, one conjunction.
STEP 4 — When or if? (5 min): Give students six situations and ask them to choose 'when' or 'if'. Make some clearly certain (the sun will rise tomorrow) and some clearly conditional (they might pass the exam). Discuss border cases where both feel possible.
STEP 5 — Consolidate: fix and write (5 min): Give each student two tasks: correct one fragment on the board, then write one complete sentence using a subordinating conjunction of their choice. Students share their sentences. The class checks: is the dependent clause attached to a main clause? Is there a conjunction collision? Is the comma in the right place?
Use directly in class — copy, adapt, or read aloud. No printing needed.
For each strategy, choose the option that best describes where you are now.
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