sister-in-law
Americannoun
plural
sisters-in-law-
the sister of one's spouse.
-
the wife of one's brother or sister.
-
the wife of one's spouse's sister or brother.
noun
-
the sister of one's husband or wife
-
the wife of one's brother
Etymology
Origin of sister-in-law
First recorded in 1400–50; late Middle English syster in lawe; sister, 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.
Jamshidi has family members, including his brother—who worked in a high-risk post as a security guard for the U.S. consulate in Herat, Afghanistan, for years—his sister-in-law, niece and nephew stuck in Camp As Sayliyah.
From The Wall Street Journal • Apr. 7, 2026
The employee was his sister-in-law, the person confirmed.
From Los Angeles Times • Feb. 18, 2026
However, detective work by his sister-in-law tracked down a social media profile for Patrick Hanna.
From BBC • Feb. 17, 2026
My sister-in-law Eva Rose, who also lives nearby and also came to the intersection separately, described to me the moment the agents’ anger was unleashed a second time as she arrived 15 minutes later.
From Slate • Jan. 25, 2026
“So, you’re my sister-in-law now?” said Percy, shaking hands with Fleur as they hurried off toward the staircase with Bill, Fred, and George.
From "Harry Potter and the Deathly Hallows" by J.K. Rowling
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.
