Likelihood based on conditions (Part 1)

Conditional sentences talk about a condition (usually introduced by if) and a possible result or consequence. The if-clause can be before or after the result clause. We use a comma between clauses when the if-clause comes first. Either clause can be positive or negative.

1. Zero conditional

If + present tense + present tense	If you heat water to 100°C, it boils.
present tense + if + present tense	Water boils if you heat it to 100°C

We use the zero conditional to talk about something that is a general truth or fact (if has a similar meaning to every time):

If you own a car, you also have to pay for insurance and registration every year.

If it is no longer a fact we use the past tense:

When I was a child, if I helped my mother, she gave me extra pocket money.

2. First conditional

If + present tense, + will/won’t (might/could/going to) + verb	If I invest my money, it will grow
will/won’t (might/could/going to) + verb + if + present tense	My money will grow if I invest it.

We use the first conditional to talk about something we feel is a probable future result:

If you leave your money in the bank, you won’t earn any interest and it may lose value over time.

We can use might, could, or may instead of will to suggest something is less probable:

If I invest it, I might lose it all.

or can to mean sometimes:

If you travel at rush hour, the trains can be very crowded. (this sometimes happens)

3. Second conditional

If + past tense, would(n’t) (might/could) + verb	If I invested my money, it would grow.
would(n’t) (might/could) + verb + if + past tense	My money would grow if I invested it.

We use the second conditional to talk about imaginary, impossible or unlikely situations in the present or future. The past tense does not refer to past time:

If I went travelling, I wouldn’t have any money left over.

⚠️With the verb be we can use was or were with I/he/she/it:

That’s what I would do if I were/was you.

We can use was/were + to-infinitive to refer to unlikely actions in the future:

If you were to spend a year travelling around the world, you’d probably need an awful lot more money than this!

4. Other words to introduce a condition

We can use other words such as when, provided that, in case, so/as long as and unless instead of if in zero, first and second conditional sentences.

When; as soon as

We use when and as soon as instead of if to show that something is more likely:

I’ll give you a lift into town if I finish my work in time. (= I am not sure if I will be able to give you a lift)
I’ll give you a lift into town when/as soon as I finish this work. (= I will give you a lift)

Unless

We use unless to show a negative condition, with a similar meaning to if…not:

You won’t earn much interest unless you invest it properly. (= If you don’t invest it properly)

Provided/providing that; so/as long as

These phrases can be used instead of if for emphasis. Provided/providing that are more common in written than spoken English:

You won’t lose any money provided that you think of it as long-term investment. (= if you think)
As long as you get a second-hand car, you should still be able to invest some money. (= if you get)

In case

We use in case to talk about precautions. Compare:

You should keep this reference number in case there are any problems. (= keep the reference number because there might be problems later)
You should quote this reference number if there are any problems. (= quote this reference number at the time of any problems)

⚠️We don’t usually start a sentence with in case.