to say or write that something is true, correct etc

declare the truth of something

to declare (something) openly

state; profess

to declare that one has (beliefs, likes, ignorance, interests etc)

declare, assert

to use bad, obscene, language; to state or promise (something) seriously and formally

declare under oath

of swear

declare under oath

to give evidence; to be evidence of (something)

vouch for; give testimony

to be responsible for; express confidence, in a person, a person's character

give assurance