1. Form

In 'zero' conditional sentences, the tense in both parts of the sentence is the simple present:


If + simple present
If you heat ice
If it rains

simple present
it melts.
you get wet

NOTE: The order of the clauses is not fixed - the 'if' clause can be first or second:


  • Ice melts if you heat it.
  • You get wet if it rains.

2. Function

In these sentences, the time is now or always and the situation is real and possible. They are used to make statements about the real world, and often refer to general truths, such as scientific facts.


  • If you freeze water, it becomes a solid.
  • Plants die if they don't get enough water.
  • If my husband has a cold, I usually catch it.
  • If public transport is efficient, people stop using their cars.
  • If you mix red and blue, you get purple.

This structure is often used to give instructions, using the imperative in the main clause:


  • If Bill phones, tell him to meet me at the cinema.
  • Ask Pete if you're not sure what to do.

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