noun

A sister-in-law is a relative gained through marriage and can be defined in two ways:

1. The Sister of a Spouse: This is when the sister is a blood relative of one's spouse. For example, if you are married and your spouse has a sister, she is your sister-in-law.
2. The Wife of a Sibling: This is when a person's sibling (either brother or sister) is married, and their spouse is the sister-in-law. For example, if your brother is married, his wife is your sister-in-law.

Sister-in-laws can play various roles in one's life, from being close friends to merely acquaintances, depending on individual family dynamics and relationships.

Example

1. Every Thanksgiving, my sister-in-law brings her famous apple pie.
2. I borrowed a dress from my sister-in-law for the wedding.
3. We celebrated my sister-in-law's birthday with a surprise party.