Adverbs of Certainty

Adverbs of certainty express how certain or sure we feel about an action or event.

Usage

Common adverbs of certainty:

certainly , definitely, probably, undoubtedly, surely

1. Adverbs of certainty go before the main verb but after the verb 'to be':

He definitely left the house this morning. 

He is definitely in the house this morning.

The news probably influences many people

He is probably in the park.

2. With other auxiliary verb, these adverbs go between the auxiliary and the main verb:

He has certainly forgotten the meeting. 

He will probably remember tomorrow.

3. Sometimes these adverbs can be placed at the beginning of the sentence:

Undoubtedly, Winston Churchill was a great politician. 

 Certainly, we will move to the city.

BE CAREFUL! with surely. When it is placed at the beginning of the sentence, it means the speaker thinks something is true, but is looking for confirmation: 

Surely, you've got a sport car?

Surely, you're OK?