As nouns the difference between vow and oblate
is that
vow is a solemn promise to perform some act, or behave in a specified manner, especially a promise to live and act in accordance with the rules of a religious order while
oblate is (roman catholic church) a person dedicated to a life of religion or monasticism, especially a member of an order without religious vows or a lay member of a religious community.
As a verb vow
is (ambitransitive) to make a vow; to promise.
As an adjective oblate is
flattened or depressed at the poles.