completely

certainly, without question

a statement (e.g. a promise) made to give confidence

statement to relieve doubt

something that is certain

positive assurance

a formal promise or agreement that certain conditions agreed (e.g. when one buys something) will be fulfilled

pledge, promise

that cannot be disputed

certain

that cannot be disputed

beyond dispute

used to make one's statement, agreement etc stronger; used to make a statement of thanks stronger; used as a comment to show interest, surprise etc

actually

that cannot be attacked and defeated

certain

undoubtedly true

definite, proven

true

actually

yes

agreed

(used as a short addition or in short answers or express agreement, approval, consent etc)

agreed