mother-in-law

American  

[muhth-er-in-law] / ˈmʌð ər ɪnˌlɔ /

noun

plural

mothers-in-law

1. the mother of one's spouse.

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mother-in-law British  

noun

1. the mother of one's wife or husband

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Etymology

Origin of mother-in-law

First recorded in 1350–1400; Middle English moder in lawe; mother ¹ ( def. ), in ( def. ), law ¹ ( def. ); 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

"My mother-in-law is dead, my brother-in-law's wife too, and their son," said a man who did not want to give his name, adding that they all lived in the same building.

From Barron's • Apr. 8, 2026

In 2019, my mother-in-law suffered a stroke and moved into our home while she recovered.

From Los Angeles Times • Apr. 3, 2026

Or will I end up being the mother-in-law to a Chatbot?

From The Wall Street Journal • Mar. 29, 2026

"My mother-in-law and I noticed that the patient did not seem to be moving," she said.

From BBC • Mar. 4, 2026

This was not the eighteen-foot-deep cellar of her mother-in-law, but perhaps it would keep the rest of her food from Jello.

From "Julie of the Wolves" by Jean Craighead George

Related Words

• aunt
• cousin
• father
• folk
• mother
• niece
• sibling
• uncle