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.
At the hospital outside General Santos, Lourdes Camia said she believed her brother-in-law, who was being treated for a heart attack, was safer outside -- despite the heat.
From Barron's • Jun. 9, 2026
The Princess of Wales's brother-in-law has told a planning inquiry his family home needs a higher level of security in a row over part of its drive being designated a public footpath.
From BBC • May 28, 2026
At one point, Spaeny looked over to see her brother-in-law having a heart-to-heart with Melton’s dad.
From Los Angeles Times • May 27, 2026
While the ceremony itself remained private with reportedly just Anderson’s twin sister as a witness and brother-in-law as officiant, the absence underscored how closely the Trump family continues to be scrutinized even in personal milestones.
From Salon • May 23, 2026
When Toussaint L’Ouverture led a revolt of black Haitian slaves in 1801, Napoleon sent his brother-in-law, General Charles LeClerc, and a military force of approximately 29,000 to crush the rebels.
From "An American Plague: The True and Terrifying Story of the Yellow Fever Epidemic of 1793" by Jim Murphy
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.
