affirm

To agree, verify or concur; to answer positively.

To assert positively; to tell with confidence; to aver; to maintain as true.

To support or encourage.

To make firm; to confirm, or ratify; especially (law) to assert or confirm, as a judgment, decree, or order, brought before an appellate court for review.

(law) To state under a solemn promise to tell the truth which is considered legally equivalent to an oath, especially of those who have religious or other moral objections to swearing oaths; also solemnly affirm.