oath

noun, plural oaths [ohthz, ohths] /oʊðz, oʊθs/.

1. a solemn appeal to a deity, or to some revered person or thing, to witness one’s determination to speak the truth, to keep a promise, etc.: to testify upon oath.
2. a statement or promise strengthened by such an appeal.
3. a formally affirmed statement or promise accepted as an equivalent of an appeal to a deity or to a revered person or thing; affirmation.
4. the form of words in which such a statement or promise is made.
5. an irreverent or blasphemous use of the name of God or anything sacred.
6. any profane expression; curse; swearword: He slammed the door with a muttered oath.

Idioms

7. take an oath, to swear solemnly; vow.

noun plural oaths (əʊðz)

1. a solemn pronouncement to affirm the truth of a statement or to pledge a person to some course of action, often involving a sacred being or object as witnessRelated adjective: juratory
2. the form of such a pronouncement
3. an irreverent or blasphemous expression, esp one involving the name of a deity; curse
4. on oath, upon oath or under oath
   1. under the obligation of an oath
   2. lawhaving sworn to tell the truth, usually with one’s hand on the Bible
5. take an oath to declare formally with an oath or pledge, esp before giving evidence

n.Old English að “oath, judicial swearing, solemn appeal to deity in witness of truth or a promise,” from Proto-Germanic *aithaz (cf. Old Norse eiðr, Swedish ed, Old Saxon, Old Frisian eth, Middle Dutch eet, Dutch eed, German eid, Gothic aiþs “oath”), from PIE *oi-to- “an oath” (cf. Old Irish oeth “oath”). In reference to careless invocations of divinity, from late 12c.