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
Noun Inflected 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
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
Helping his brother-in-law film a documentary, Thapar watched as their subject stalked a herd of sambar deer in one of the many Ranthambore lakes.
From The Wall Street Journal • Apr. 21, 2026
Muldoon is survived by his partner, Miriam Rothbart; parents Deanna and Patrick Muldoon Sr, his sister and brother-in-law Shana and Ahmet Zappa, niece Halo and nephew Arrow Zappa.
From BBC • Apr. 20, 2026
It’s also possible for a lawyer to be just plain stupid, isn’t it? 6TH JUROR: YOU sound like you’ve met my brother-in-law.
From "Twelve Angry Men" by Reginald Rose
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.
