Adverbials of probability
可能性状语

We use adverbials of probability to show how certain we are about something. The most frequent adverbials of probability are:
我们用可能性状语表示我们队对某件事的确定程度。最常用的可能性状语有：

certainly - definitely - maybe - possibly

clearly - obviously - perhaps - probably

maybe and perhaps usually come at the beginning of the clause:
maybe 和perhaps 通常在句首出现：

Perhaps the weather will be fine.

Maybe it won’t rain.

Other adverbs of possibility usually come in front of the main verb:
其他可能性副词经常出现在主要动词的前面：

He is certainly coming to the party.

Will they definitely be there?

We will possibly come to England next year.

but in after am, is, are, was, were:
但是可能性状语要在be动词后面:

They are definitely at home.

She was obviously very surprised.