誓う

swear, swear an oath: 正式にまたは宣誓して誓うこと.

vow: 公にまたはおごそかに誓うこと.

pledge: 特に重責を担う個人・団体・政府機関などが人に固く約束すること.

source: Romeo x Juliet | Wedding Vows on Make a GIF

a solemn promise.

«…する/…の» (神かけての)誓い, 誓約 «to do/of»

(vows) a set of promises committing one to a prescribed role, calling, or course of action, typically to marriage or a monastic career.

〖通例～s〗 (結婚や修道生活に入るに際して行う)誓い, 誓約

1. reporting verb solemnly promise to do a specified thing:

｟かたく･主に文｠ ; 〖～ to do/(to A) (that)節〗 …すると, (A〈人〉に)…ということを誓う, 誓約する; ｟かたく｠ …を誓う

e.g. with clause : he vowed that his government would not tolerate a repeat of the disorder

｟書 ｠ 〖直接話法〗…と誓う

e.g. with direct speech : one fan vowed, “I'll picket every home game.”.

2. with object archaic dedicate to someone or something, especially a deity:

｟かたく･古｠ (誓いを立てて) «…に» …をささげる «to»

e.g. I vowed myself to this enterprise.

Middle English: from Old French vou, from Latin votum (see vote); the verb is from Old French vouer.