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Grammar6 min read

Conditional Sentences: If, When, Unless Explained

The four conditionals, plus if vs when vs unless — clear forms, real uses, and the backshift error that lowers CLB writing scores.

Conditionals let you talk about possibilities, consequences, advice, and regret — high-value structures for CELPIP/IELTS speaking and writing. Most errors come from mixing up the four types or misusing if/when/unless. Here is the clear map.

The Four Conditionals

TypeUseFormExample
ZeroGeneral truths / factsIf + present, present"If you heat water, it boils."
FirstReal future possibilityIf + present, will + base"If it rains, I will stay home."
SecondUnreal / unlikely present or futureIf + past, would + base"If I had more time, I would study."
ThirdUnreal past (regret)If + past perfect, would have + participle"If I had studied, I would have passed."

How to Choose Quickly

  1. Is it always true? → Zero.
  2. Is it a real future possibility? → First.
  3. Is it imaginary/unlikely now? → Second.
  4. Is it about the past that cannot change? → Third.

Mixed Conditionals

Real life mixes time frames. A past condition with a present result:

"If I had taken that job (past), I would be in Vancouver now (present)." This shows advanced control — useful for higher CLB bands.

If vs When vs Unless

  • If = it may or may not happen: "If he calls, tell him I’m out."
  • When = it will definitely happen, just not sure exactly when: "When he calls, tell him…" (you expect the call).
  • Unless = "if not / except if": "I won’t go unless you come." (= if you do not come, I won’t go).

Using "when" for an uncertain event ("When I win the lottery…") changes your meaning — choose deliberately.

The Errors That Cost Marks

  1. "will" in the if-clause: ✗ "If it will rain…" → ✓ "If it rains…"
  2. Wrong backshift in second conditional: ✗ "If I would have time…" → ✓ "If I had time…"
  3. Mixing third conditional form: ✗ "If I would have known…" → ✓ "If I had known…"
  4. Double negative with unless: ✗ "Unless you don’t hurry…" → ✓ "Unless you hurry…"

Practice That Works

Do not drill all four at once. Take real situations from your life and say them in the correct conditional: a future plan (first), a wish (second), a regret (third). Speaking your own true sentences fixes conditionals faster than gap-fill exercises — and get feedback on the if-clause verb, where most errors hide.

Bottom Line

Identify the time and reality (fact / real future / unreal now / unreal past), pick the matching conditional, keep "will" and "would" out of the if-clause, and choose if/when/unless by meaning. Used accurately, conditionals are an easy way to show range on the CLB writing and speaking bands.

Tags:

#Grammar#Conditionals#Writing#CLB

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