uncle

alt=1929 photograph of United States Representative Charles A. Eaton and his nephew Rep. William R. Eaton.|thumb|United States Representative Charles Aubrey Eaton|Charles A. Eaton (right) and his nephew Rep. [[William R. Eaton (left)]] An uncle is usually defined as a male relative who is a sibling of a parent or married to a sibling of a parent, as well as the parent of the cousins. Uncles who are related by birth are second-degree relatives. The female counterpart of an uncle is an aunt, and the reciprocal relationship is that of a nephew or niece. The word comes from , the diminutive of avus (grandfather), and is a family relationship within an extended or immediate family. A popular colloquial term in English is Unc.

In some cultures and families, children may refer to the cousins of their parents as uncle (or aunt). It is also used as a title of respect for older relatives, neighbours, acquaintances, family friends, and even total strangers in some cultures, for example Aboriginal Australian elders. Using the term in this way is a form of fictive kinship.