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.
Uncles by birth (brother of a parent) are related to their nieces and nephews on average by 25% (1750 centimorgans) though this can vary considerably.
Instead, there are specific terms describing a person's kinship to their mother's brother (dajë in Albanian, daiyee in Persian, wuj (diminutive: wujek) in Polish) or a person's kinship to their father's brother (xhajë in Albanian, amou in Persian, stryj (diminutive: stryjek) in Polish).
An analogous differentiation exists using separate terms to describe a person's kinship to their mother's female sibling (teze in Albanian, khaleh in Persian, ciotka (diminutive: ciocia) in Polish), and a person's kinship to their father's female sibling, (hallë in Albanian, ammeh in Persian, stryjna (diminutive: stryjenka) in Polish).
For example, there is a specific term describing a person's kinship to the spouse of their paternal uncle (i.e. zan-amou, literally 'wife-of-' amou).
This clarifies that kinship is to the spouse of the person's paternal male sibling, as opposed to a blood-relationship.
In Tibetan mythology Akhu Tönpa (Uncle Tompa) is a familiar and well-beloved figure.