brother-in-law
Americannoun
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the brother of one's spouse.
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the husband of one's sister or brother.
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the husband of one's spouse's sister or brother.
noun
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the brother of one's wife or husband
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the husband of one's sister
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the husband of the sister of one's husband or wife
Other Word Forms
Etymology
Origin of brother-in-law
First recorded in 1350–1400; Middle English brother in law(e); see origin at brother, in, law 1; from Middle English in-lawe “in law,” i.e., “a person within the regulation and protection of the law,” based on the prohibition by Roman civil law and, later, Christian canon law, of marriages within four degrees of consanguinity, i.e., up to and including first cousins
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
"I'd phoned my brother-in-law just to see if there was a bit of a space for the evening and I was trying to gather some things together for my wife as well."
From BBC • Apr. 27, 2026
Roxanne lived in a double-wide trailer with her husband, plus her parents-in-law and brother-in-law.
From Salon • Apr. 19, 2026
Ahmad said that those were photos from a trip to see his brother-in-law, who was training at a U.S. military base.
From Slate • Apr. 19, 2026
She eventually tracks down other Blumstein relations who had landed in Israel, finding them living in the same town as Ms. Gerson’s brother-in-law.
From The Wall Street Journal • Apr. 7, 2026
Gardenia’s brother-in-law told Bobbette that Henrietta’s cells had been all over the news lately because they’d been causing problems by contaminating other cultures.
From "The Immortal Life of Henrietta Lacks" by Rebecca Skloot
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
