Conditionals — Zero, First, and Second

Conditional sentences talk about what happens or could happen under certain conditions. The zero conditional describes facts and habits, the first conditional talks about realistic future possibilities, and the second conditional imagines unlikely or hypothetical situations.

What are Conditionals?

Conditional sentences have two parts:

if-clause (the condition)
main clause (the result)

If it rains, I will stay home.

Zero Conditional — General Truths and Habits

Structure: If + present simple → present simple

Used for facts, scientific truths, and things that are always true:

If you heat water to 100°C, it boils. If I eat too much sugar, I get a headache.

Note

You can replace if with when in zero conditionals without changing the meaning: When you heat water to 100°C, it boils.

First Conditional — Real Future Possibility

Structure: If + present simple → will + infinitive

Used for things that are likely or possible in the future:

If it rains tomorrow, we will cancel the picnic. If you study hard, you will pass the exam. She will be late if she misses the bus.

Warning

Do not use will in the if-clause! ✗ If it will rain, we will cancel the picnic. ✓ If it rains, we will cancel the picnic.

Second Conditional — Hypothetical / Unlikely

Structure: If + past simple → would + infinitive

Used for imaginary, unlikely, or impossible situations in the present or future:

If I had a million euros, I would travel the world. If she were a scientist, she would discover something amazing. I would help you if I knew the answer.

Note

In the second conditional, we often use were for all subjects (especially in formal writing): If I were you, I would apologise.

Summary Table

Type	If-clause	Main clause	When to use
Zero	present simple	present simple	facts/habits
First	present simple	will + infinitive	real future possibility
Second	past simple	would + infinitive	hypothetical/unlikely

Real world: safety instructions (zero conditional)

"If the alarm sounds, evacuate the building immediately." "If you feel unwell, do not come into work." "If the temperature drops below 0°C, water freezes."

Real world: email / planning (first conditional)

"If the delivery arrives before Friday, we will be able to dispatch your order on time." "If it rains at the weekend, the outdoor event will move inside."

Real world: expressing wishes / dreams (second conditional)

"If I had more time, I would learn to play the piano." "If you were the manager, what would you change?"

Tip Conditionals are everywhere: safety signs (zero), weather-dependent plans and emails (first), and expressing wishes or polite suggestions (second). Look for "If …" clauses in instruction manuals, contract terms ("If payment is not received…"), and everyday conversations.

Practice Problems

Which conditional is this? 'If I won the lottery, I would buy a house.'

Show answer

Second conditional. The situation is hypothetical (imagining winning the lottery). Structure: If + past simple (won) + would + infinitive (would buy).

Complete: 'If you mix red and blue, you __ purple.' (zero conditional)

Show answer

'get' — If you mix red and blue, you get purple. (general truth, present simple + present simple)

Correct the mistake: 'If it will snow tomorrow, we will go skiing.'

Show answer

'If it snows tomorrow, we will go skiing.' (First conditional — use present simple in the if-clause, not 'will')