Common adverbs of certainty:
1. Adverbs of certainty go before the main verb but after the verb ‘to be’:
- He definitely left the house this morning.
- 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.
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 bicycle?