When a person's niece or nephew has a female child, the child is the grandniece of that individual. A grandniece is also referred to as a great niece.
A person who has a grandniece can be referred to as a great aunt or great uncle. The siblings of the parents of the female child are simply referred to as aunts and uncles by the child. The great aunt or uncle of the parents of the female child is the child's great-great aunt or uncle. "Great grandniece" is the term used to refer to the female grandchild of a person's niece or nephew.