Functions and notions

Likelihood

We can use modal verbs and non-modal expressions to talk about the possibility of something happening or being true.

Modal verbs

Will and would

If we think something is certain to be true or not true we use will, won't, would and wouldn't.

• The asteroid will miss us.
• Scientists announced that the asteroid wouldn't hit Earth.
• If you saw someone in the building, it will have been the security guard.

Should

If we think something is probably true or not true, and that this situation is desirable, we use should and shouldn't.

• It should be a nice day tomorrow.
• There shouldn't be any problems, but if there are, just call me.

May, might and could

If we think something is possibly true or not true, we use may, might, could, might not and may not. We don't use couldn't.

• We might not play baseball – it depends on the weather.
  NOT: We couldn't play baseball – it depends on the weather.

Cannot and couldn't

If we think it is impossible that something is true we use cannot/can't and couldn't.

• That can't be John – he's in Australia.
• You couldn't have seen that movie – it hasn't come out yet!

Must

If circumstances strongly suggest that something is true we use must.

• She came to work today, so she must be feeling better.

To talk about the likelihood of a situation in the past, the modal verbs above are followed by a perfect infinitive.

• She's not normally late. I suppose she may have gotten stuck in traffic.
• He speaks good Spanish. He must have been studying for years.

Non-modal expressions

A large variety of non-modal expressions are used to talk about the likelihood of something being true.

Expressions like The chances of …, which refer to the statistical probability of something happening, can be used to talk about different degrees of likelihood.

• The chances of the asteroid hitting Earth are very small.
• The probability of you getting the job is very high.
• There is a 1,000-1 chance that the asteroid will hit Earth. (= 0.1%)
• There's a 2-1 chance that our dog will win the race. (= 50%)
• The odds against them qualifying for the final are enormous. (= the probability of qualifying is low)
• The odds against you being selected are very low. (= the probability of being selected is high)
• I think they stand a good chance of winning.
• If an asteroid hit Earth we wouldn't stand a chance of surviving.

• Chances are he'll get a very bad reference.
• Yeah, I expect you're right.

Adverbs and adjectives

Adverbs like possibly, probably, definitely, maybe and perhaps can be used to talk about the likelihood of something being true.

• Maybe it's too cold for the plant to grow in here.
• She definitely won't be at the meeting.
• The job's probably going to finish in May.

The adjectives likely, unlikely, bound, certain and sure followed by an infinitive are used to talk about the likelihood of something being true.

• You're unlikely to find a cheaper apartment than this.
• The Giants are bound to win the next World Series. (= it's highly probable)
• The weather forecast said it's certain/sure to rain tomorrow.