sister-in-law

American  

[sis-ter-in-law] / ˈsɪs tər ɪnˌlɔ /

noun

plural

sisters-in-law

1. the sister of one's spouse.

2. the wife of one's brother or sister.

3. the wife of one's spouse's sister or brother.

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sister-in-law British  

noun

1. the sister of one's husband or wife

2. the wife of one's brother

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Etymology

Origin of sister-in-law

First recorded in 1400–50; late Middle English syster in lawe; see origin at 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

Then, another option is the Eastside, where Michelle is from and where the family moved to in 2020, at the suggestion of a sister-in-law, for Kevin’s enhanced therapeutic services.

From Los Angeles Times • May 8, 2026

Giuffre's sister-in-law, Amanda Roberts, said they did not have to go "deep into conversation" given the potential complications of impeding investigations.

From BBC • Apr. 24, 2026

A sister-in-law “thinks I don’t like her,” she crabbily notes.

From The Wall Street Journal • Apr. 23, 2026

Another social media user has reported that the textile company where their sister-in-law worked has fired 600 out of their 650 personnel, as they cannot import raw material from Australia anymore.

From BBC • Apr. 21, 2026

She was as uninterested in it as she was in her trousseau, and she left all decisions in the hands of her fiance and her future sister-in-law.

From "The House of the Spirits: A Novel" by Isabel Allende

Related Words

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