To affirm to be correct, true, or genuine.

"When will the appraiser attest the date of the painting?"

To certify by signature or oath.

"You must attest your will in order for it to be valid."

To certify in an official capacity.

To supply or be evidence of.

"Her fine work attested her ability."

To put under oath.

To call to witness; to invoke.

Proven; shown to be true with evidence

Supported with testimony

Certified as good, correct, or pure

Of words or languages, proven to have existed by records.

"The word slæpwerig (sleep-weary) is attested in the Exeter Book in the form slæpwerigne."