Definitions for "Niece"
A relative, in general; especially, a descendant, whether male or female; a granddaughter or a grandson.
A daughter of one's brother or sister, or of one's brother-in-law or sister-in-law. In modern English, this is the primary meaning.
Up until the 1600’s this meant a descendant, either male or female. Occasionally it was used to mean any younger relative.