To make a solemn oath by invoking something sacred or deeply valued as a guarantee of truth.
To promise something is true by mentioning something very important to you, like your mother's life or the Bible.
2 meanings, ordered from most common to least. Color-coded by CEFR level.
To make a formal or legal oath by placing one's hand on a sacred object (such as a Bible) as a sign of sincerity.
"The witness swore on the Bible before giving his testimony in court."
I do solemnly swear on the Constitution of the United States.
— Traditional U.S. presidential oath of office formula.
To promise informally that something is absolutely true by invoking something precious to you.
"I swear on my life that I never touched your phone."
To place a sworn oath upon something — resting your promise on an object or person of great importance.
To promise something is true by mentioning something very important to you, like your mother's life or the Bible.
Used in legal, religious, and everyday informal contexts. Common collocations include 'swear on the Bible,' 'swear on my mother's grave,' and 'swear on my life.' The casual version ('I swear on my life') is very common in informal speech.
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