in-law

American  

[in-law] / ˈɪnˌlɔ /

noun

1. a relative by marriage.

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in-law British  

noun

1. a relative by marriage

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adjective

1. (postpositive; in combination) related by marriage

   a father-in-law

Etymology

Origin of in-law

First recorded in 1890–95; back formation from mother-in-law, brother-in-law, etc.

Explanation

An in-law is someone who is a relative because of marriage, like your husband's sister or your wife's father. You can refer to your spouse's entire family as your in-laws. In some countries, a married woman moves in with her in-laws, symbolically becoming part of their family. In the U.S. some families live with extended family members — a man may live with his wife, kids, and his mother- and father-in-law — but more often each individual nuclear family lives separately. In-law originally meant "anyone of a relationship not natural" or "not by blood."

Example Sentences

There’s also a lower-level lounge, media room, wine cellar, an in-law suite, and a home gym.

From MarketWatch • Nov. 26, 2025

The presence of the surly uncle, insufferable in-law, or grating girlfriend at the holiday table can make it hard to truly count one’s blessings.

From The Wall Street Journal • Nov. 21, 2025

She might be your aunt or an in-law.

From Salon • Oct. 16, 2025

Ofri Bibas Levy, Yarden's sister, added: "My brother returned, but my sister in-law and nephews have not. Yarden asks about them and I have no answers for him."

From BBC • Feb. 3, 2025

Now she was acting like an in-law, like an aunt, dabbling at helping Ruth and the girls, but having no interest in or knowledge of decent housekeeping, she got in the way.

From "Song of Solomon" by Toni Morrison