What's the difference between zero and first conditional?

Zero conditional describes things that are always true ('If you heat ice, it melts'). First conditional describes a specific likely future situation ('If it rains tomorrow, we'll stay home'). Zero = always; first = a specific future possibility.

Can I use 'when' instead of 'if' in zero conditionals?

Yes — for things that always happen, 'when' and 'if' are nearly interchangeable: 'When/If you heat water to 100°C, it boils'. 'When' implies it definitely happens regularly; 'if' is slightly more conditional but still general. Both are correct for general truths.

Why is 'If you heat ice, it will melt' wrong for zero conditional?

Because zero conditional describes a fact, not a future prediction. Use present simple in both clauses: 'If you heat ice, it melts'. Adding 'will' shifts it toward first conditional, which talks about specific future outcomes rather than always-true truths.

Can I use zero conditional for personal habits?

Yes, when the result is automatic and predictable: 'If I drink coffee at night, I can't sleep' or 'When I'm tired, I get grumpy'. These work because the cause and effect are reliable patterns, just like a scientific law on a smaller scale.

Do I need a comma between the clauses?

Yes, when the if-clause comes first: 'If you heat water, it boils'. No comma when the if-clause comes second: 'Water boils if you heat it'. The same comma rule applies to all conditional types — first, second, third, and mixed.

Zero Conditional

General truths and facts: If/When + present, present

Last updated 13 June 2026

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The zero conditional describes general truths, scientific facts, and predictable results — situations where the condition always leads to the same outcome. Both clauses use the present simple, often with 'if' or 'when' interchangeably.

When to Use Zero Conditional

•Scientific facts: If you heat water to 100°C, it boils.
•General truths: If you don't eat, you get hungry.
•Instructions/rules: If the alarm sounds, leave the building.
•Habits with predictable results: When I drink coffee, I can't sleep.
•Cause and effect that is always true.

How to Form Zero Conditional

Affirmative (+)

If/When + present simple, present simple

Negative (-)

If/When + present simple (neg), present simple

Question (?)

What happens if + present simple?

💡 Both clauses use present simple. 'When' can replace 'if' for things that always happen.

Examples of Zero Conditional

✓If you mix red and blue, you get purple.

✗If you mix red and blue, you will get purple.

Zero conditional uses present in both clauses for facts.

✓When water freezes, it expands.

✗When water freezes, it will expand.

General truths use present, not will.

✓If I eat too much, I feel sick.

✗If I eat too much, I felt sick.

Keep both clauses in present simple.

Common Mistakes with Zero Conditional

💡 Practice Tips for Zero Conditional

• Pattern: If/When + present, present.
• Use for facts, scientific laws, and always-true habits.
• Contrast with first conditional (real future possibility).
• When = if for things that always happen; if = possibility.

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When to Use Zero Conditional

How to Form Zero Conditional

Examples of Zero Conditional

Common Mistakes with Zero Conditional

✗If you heat ice, it will melt.

✗If I am tired, I went to bed.

✗When the sun rise, it gets light.

💡 Practice Tips for Zero Conditional

Frequently Asked Questions about Zero Conditional

What's the difference between zero and first conditional?

Can I use 'when' instead of 'if' in zero conditionals?

Why is 'If you heat ice, it will melt' wrong for zero conditional?

Can I use zero conditional for personal habits?

Do I need a comma between the clauses?

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