Synonyms for Vow:

n.

give (someone) your word, vouchsafe, undertake. solemn word, word of honor, warrant, guaranty, word, plight. promise (noun)
engagement, asseveration, mutual agreement, pact, agreement, pledge, understanding, assurance, obligation, arrangement, covenant, compact, bond, contract, word of honor, affiance, oath, stipulation.
promises (noun)
commitment.
vow (noun)
consecrate.
word (noun)
word.
word of honor (noun)
pledge.

v.

communication (verb)
consecrate.
make a solemn promise (verb)
covenant, swear, promise, warrant, consecrate, plight, assure.
promise (verb)
assure, swear, guarantee, consent, promise, agree, stipulate, pledge.

Other synonyms:

solemn word, word of honor. undertake. guaranty. warrant. word. agree
covenant.
promise
assure.
Other relevant words:
commitment, plight, undertaking, consecrate, vouchsafe, word, asseveration, affiance, warrant, solemn word, undertake, guaranty, word of honor.

Usage examples for vow

  1. " That is a 'cute trick, I vow said he. – Winning His Way by Charles Carleton Coffin
  2. For not only were the brethren under vow to possess nothing whatever in the world, and not only were they forbidden to touch money on any account, but the Order itself was bound to poverty. – A Child's Book of Saints by William Canton
  3. Say it, word for word, or I shall be angry- I vow I shall. – Le Morvan, [A District of France,] Its Wild Sports, Vineyards and Forests; with Legends, Antiquities, Rural and Local Sketches by Henri de Crignelle