niece

In the language of kinship, a nephew is a son of a person's sibling, and a niece is a daughter of a person's sibling. Conversely, that person is the aunt or uncle of their niece or nephew. The relationship of aunt/uncle to niece/nephew is an example of second-degree relatives, meaning that their coefficient of relationship is 25%.
The terms are also used colloquially for sons and daughters of siblings-in-law, even though there is no blood relationship.

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