Zero & First Conditional

What it means

Conditionals are "if" sentences: if one thing happens, another thing happens. The zero conditional is for facts that are always true. The first conditional is for real, possible situations in the future.

How to make it

• Zero: If + present simple, present simple → If you heat ice, it melts.
• First: If + present simple, will + base verb → If it rains tomorrow, I will stay home.
• Short forms: will → 'll, will not → won't
• The if-part can come first or second: If I finish early, I'll call you. / I'll call you if I finish early.
• Use a comma only when the if-part comes first.
• unless = if not: Unless you study, you won't pass the exam.

When to use it

• Zero – facts and general truths: If you mix red and blue, you get purple.
• First – a real possibility in the future: If I finish work early, I'll call you.
• First – warnings: You'll miss the bus if you don't hurry.
• With unless: Unless you study, you won't pass the exam. (= If you don't study, you won't pass.)

Compare

• Zero: If you heat ice, it melts. (true every time – you can also say "when")
• First: If it rains tomorrow, I will stay home. (one possible future situation)
• In both, the if-part uses the present simple – even when we talk about the future.

Common mistakes

• ❌ If it will rain, I will stay home. → ✅ If it rains, I will stay home. (no "will" after "if")
• ❌ Unless you don't study, you won't pass. → ✅ Unless you study, you won't pass. (unless already means "if not")
• ❌ I'll call you, if I finish early. → ✅ I'll call you if I finish early. (no comma when the if-part comes second)