Sister-in-law (noun)

1. The sister of one's spouse.
2. The wife of one"s brother, or the sister of one"s spouse.

Origin:

Late 16th century: from sister + in-law (from the former legal use of in-law to mean "related by marriage").

Examples:

1. He went to visit his sister-in-law.
2. His sister-in-law was very kind to him.
3. Her sister-in-law was her best friend.
4. He introduced his sister-in-law to his friends.
5. He went to his sister-in-law's wedding.