Certainty In Certain

I am certain.
 I could be certain.
I have certain
 I know certain

Thus goes the certain
 as I am certain
what I do is certain
 what not is certain.

Certain things fit
 Certain ideas are good
 certain conditions are appropriate
 certain in a way certain.

certain is at times infinite
 most times it is definite
 that way is certain
 a certainty in certain.