Adverbs of Probability

Adverbs of probability tell us how certain or uncertain we are that something is true or that something will happen.

They are common in everyday English and particularly useful for Cambridge B2 First (FCE) and C1 Advanced (CAE), where you often need to express opinions, make predictions and discuss possibilities.

In this lesson, you will learn how to use definitely, certainly, surely, probably, possibly, perhaps and maybe, as well as the common structures be likely to and be unlikely to.

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Adverbs of Probability: From Certain to Uncertain

You can think of these words as being on a scale:

Very certain	definitely, certainly
Strong expectation	surely
Quite likely	probably
Possible	possibly
Uncertain	perhaps, maybe
Not very likely	unlikely

The exact degree of certainty depends on the situation and the speaker, so these are not fixed percentages.

Definitely

Definitely means without any doubt. We use it when we feel very certain that something is true or will happen.

• We should definitely visit Edinburgh while we’re in Scotland.

It normally comes before the main verb:

• I definitely agree with you.

But it comes after the verb be:

• She is definitely the best person for the job.

With auxiliary verbs, it normally comes after the auxiliary:

• They will definitely arrive before six.

Certainly

Certainly also expresses a high degree of certainty and is close in meaning to definitely.

• Sally certainly deserves some recognition for her work.

Certainly can sound slightly more formal than definitely, so it is particularly useful in written English.

Surely

Surely is slightly different.

We often use it when we believe something must be true and expect the other person to agree.

• Surely there must be another explanation.

Probably

Probably means that something is more likely to happen than not.

It is one of the most useful adverbs of probability in English.

• They will probably arrive late because of the traffic.

Probably + negative

We usually say: He probably won’t come.

rather than: He won’t probably come.

Possibly

Possibly expresses a weaker or more uncertain possibility.

• They might possibly visit us next weekend.

With could, possibly is also commonly used to make requests sound more polite:

• Could you possibly send me the document today?

Perhaps

Perhaps means maybe or possibly.

It commonly appears at the beginning of a sentence.

• Perhaps there is another solution.

Maybe

Maybe has approximately the same meaning as perhaps, but it is especially common in everyday spoken English.

• Maybe we should try a different approach.

Maybe most often appears at the beginning of a sentence.

Maybe vs may be

Be careful not to confuse maybe with may be.

Maybe is one word and means perhaps:

• Maybe he’ll come later.

May be consists of the modal verb may + be:

• He may be late.

What about Likely and Unlikely?

Learners often see likely and unlikely included in lists of adverbs of probability.

However, in sentences such as these, they are normally adjectives.

Be likely to

We use be likely to + infinitive when something will probably happen.

• She is likely to get the job.
• Prices are likely to rise next year.

We can also say:

• It is likely that she will get the job.

Be unlikely to

Unlikely expresses the opposite idea.

• She is unlikely to attend the meeting.
• The situation is unlikely to improve immediately.

These structures are extremely useful in formal and exam writing.

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Where Do Adverbs of Probability Go in a Sentence?

Sentence position is one of the most important things to learn.

1. Before the main verb

Adverbs such as probably, certainly and definitely usually appear before an ordinary main verb.

• She probably knows the answer.

2. After the verb be

When be is the main verb, the adverb usually comes after it.

• He is definitely interested.

3. After an auxiliary verb

With auxiliary and modal verbs, the adverb normally comes after the first auxiliary.]

• They have certainly improved.

4. At the beginning of the sentence

Maybe and perhaps are particularly common at the beginning.

• Perhaps they misunderstood the instructions.

Other adverbs can sometimes be moved for emphasis, but learners should first become comfortable with the most natural positions above.

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Preparing for B2 First?

Learning to express certainty and possibility accurately can also improve your writing. In my B2 First Writing books, you’ll find practical guidance and exam-style practice to help you develop clearer, more natural answers.

Common Mistakes with Adverbs of Probability

❌ She probably is tired.

✅ She is probably tired.

❌ Maybe she may come later.

✅ Maybe she’ll come later.

✅ She may come later.

❌ She likely will come.

✅ She is likely to come.

✅ It is likely that she will come.

❌ They will definite arrive early.

✅ They will definitely arrive early.

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Adverbs of Probability Quiz

Related posts:

• Modal Verbs in the Past 
• Modal Verbs of Speculation 
• B2 First Grammar 
• How to Write an Essay for B2 First (FCE) 
• B2 First Writing