cerˈtainly adverb

1. Without doubt, undoubtedly
2. In a resolved, fixed, etc manner

Yes, of course

cerˈtainty noun

1. Something certain (also in short form cert)
2. The state of being sure

cerˈtitude noun

(a) certainty

a certain person

A person known but not specifically named, implying some degree of contempt

a lady of a certain age

A woman who is no longer young

for certain

Assuredly, certainly

in a certain condition (euphemistic)

Pregnant

make certain see under make¹

moral certainty see under moral