affirm

verb

1.
establish or strengthen as with new evidence or facts
confirm corroborate substantiate support sustain
Event:
affirmation
Antonym:
negate
Derived from:
affirmable affirmation
2.
to declare or affirm solemnly and formally as true
assert aver avow swan swear verify
Agent:
affirmer
Event:
affirmation
Derived from:
affirmation affirmer
3.