ADVERBS OF CERTAINTY

Function: These adverbs express how certain or sure we feel about an action or event.

Common adverbs of certainty:
certainly, definitely, probably, undoubtedly, surely

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

Examples:
1. He definitely left the village this night.
2. He is probably in the house.

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

Examples:
1. He has certainly forgotten the meeting.
2. He will probably remember tomorrow.

Sometimes these adverbs can be placed at the beginning of the sentence
example:
1. Undoubtedly, Winston Churchill was a great politician.

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:
Example:
1.Surely you've got a motorcycle?