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 Latin: avunculus, the diminutive of avus (grandfather), and is a family relationship within an extended or immediate family. The gender-neutral term pibling, a shortened form of parent's sibling, may refer to either an aunt or an uncle.

पारिवारिक संबंधो में चाचा पिता का छोटा भाई है। चाचा एक प्राथमिक प्रेम व स्नेह का प्रतीक है बच्चा जो बात अपने माता पिता से नही कह पाता वो बाते भी चाचा से शेयर करता है । इसलिए चाचा का दर्जा भी एक महत्वपूर्ण है ।