Zero and First Conditionals

Zero and first conditionals describe real or possible situations. The key difference is whether you are describing a general result or a likely future result. Both clauses are real-world possibilities; the form shows how you connect the condition to its result.

Compare the two patterns

Zero conditional: regular results

Use the zero conditional for facts, routines, instructions, and results that usually happen whenever the condition is true. Both clauses normally use the present simple.

First conditional: real future possibilities

Use the first conditional when the condition is possible and the result belongs to the future. The if-clause uses the present simple, even though it refers to the future; the result clause can use will, an imperative, or another appropriate modal.

Put the clauses in either order

The meaning stays the same when you move the if-clause. Use a comma when the if-clause comes first, but usually not when it comes second: “If I have time, I will call you” and “I will call you if I have time.”

Choose the meaning before the form

Ask whether the result is always or usually true, or whether it is a future possibility. The verb form follows that meaning; do not choose a conditional only because it sounds familiar.

Common mistakes to check

A useful editing routine

1. Underline the condition and the result.

2. Decide whether the result is a general fact or a future possibility.

3. Check that you have not used will directly after if or unless.

4. Read the sentence aloud and check the comma when the if-clause comes first.

Practice in a real situation

1. Write one zero conditional about a habit or fact in your daily life.

2. Write one first conditional about a plan for tomorrow.

3. Change the order of the clauses and add the correct comma.

4. Replace will with might or an imperative when the meaning changes.

The conditional form is a map: it shows how certain, regular, or possible the result is.