Adverbs of certainty: A complete guide to expressing confidence in English

Adverbs of certainty show the speaker’s level of confidence in a statement. We use these modifiers to signal whether something is a definite fact or just a possibility.

What are adverbs of certainty?

Adverbs of certainty are words that describe the level of conviction a speaker has regarding a statement. They typically answer the question, “How sure are you?” Common examples include definitely, probably, and certainly.

If you are looking for a comprehensive breakdown of these rules, the English Grammar in Use by Raymond Murphy is widely considered the best self-study book for intermediate learners.

Common adverbs of certainty ranked by intensity

Where do adverbs of certainty go in a sentence?

Placement is the most common mistake for English learners. To write clearly, follow these three fundamental rules:

1. Before the main verb

If there is only one verb in the sentence (and it isn’t the verb “to be”), place the adverb directly before it.

• Correct: He certainly knows the answer.
• Incorrect: He knows certainly the answer.

2. After the verb “to be”

When using “to be” (am, is, are, was, were), the adverb follows the verb.

• Correct: They are probably late because of traffic.
• Incorrect: They probably are late.

3. Between the auxiliary and main verb

In sentences with helping verbs (will, have, can, must), the adverb sits in the middle.

• Correct: I have definitely seen that movie before.
• Incorrect: I definitely have seen that movie before.

Grammar Note: In negative sentences, “probably” usually goes before the negative word (e.g., “I probably won’t go”), whereas “certainly” can go after it.

Common mistakes to avoid

To ensure your writing is natural and grammatically sound, watch out for these frequent errors:

• Wrong placement with negative verbs: The ‘Probably’ Rule: If the sentence is negative, probably usually comes before the auxiliary (e.g., ‘I probably won’t’). Most other adverbs come after it.
• Confusing “maybe” and “may be”: “Maybe” (one word) is an adverb often used at the start of a sentence. “May be” (two words) is a verb phrase (e.g., “It may be difficult”).
• Overusing “certainly” in casual speech: In relaxed conversation, “definitely” or “totally” are more common. Save “certainly” and “undoubtedly” for formal writing or professional emails.

Visual cues help solidify these rules. These English Grammar Educational Posters are excellent for a home office or classroom to keep word order rules top-of-mind.

Frequently asked questions about adverbs of certainty

Practice quiz: Test your knowledge

Try to identify the correct placement or word choice for the following five questions.

1. Where does “definitely” go? Sentence: I (A) will (B) be (C) there.
2. Where does “probably” go? Sentence: She (A) is (B) at (C) home.
3. Where does “certainly” go? Sentence: They (A) think (B) it’s (C) a good idea.
4. Which word is best for expressing a 50% chance? A) Definitely | B) Possibly | C) Clearly
5. Which is the most natural negative sentence? A) I won’t probably go. | B) I probably won’t go.

Summary table: Quick placement guide

Conclusion: Mastering your confidence in English

Getting these adverbs in the right place makes your English sound much more natural. While the rules for negative sentences can be tricky, following the ‘To Be’ and ‘Auxiliary’ rules will solve 90% of placement errors.

Whether you are writing a professional email or chatting with friends, these small words carry a lot of weight. Start by practicing with one or two adverbs today, and soon, their placement will become second nature.

Join the conversation

Which adverb of certainty do you find yourself using the most? Or is there a specific sentence structure that still feels a bit tricky?

Leave a comment below with your thoughts or a practice sentence, and I will be happy to give you some feedback! If you found this guide helpful, please share it with a fellow English learner or colleague who might find it useful.