What's the difference between 舅舅 and 叔叔?

Question

My favorite short story in modern Mandarin, 2015 by 王小波, is basically a long, humorous digression about the author's 舅舅:

我舅舅是个无照画家，和别人不同的是，他总在忙些正事。有时他在作画；有时他卖画，并且因此蹲在派出所里。他作画时把房门锁上，再戴上个防震耳罩，别人来敲门听不见，打电话也不接，独自一人面对画架，如痴如狂。因为他住在十四层楼上，谁也不能趴窗户往里看，所以没人见过他作画，除了一个贼。

This word is translated as 'uncle.'

But why isn't the man a 叔叔? What's the difference in usage?

Answer 1

For uncles of mother's side are called 舅舅, while for uncles of father's side if he's older than your father you have to him 伯, and 叔 for younger ones. Ff you have more than one 舅 or 叔 or 伯. You need to add some prefix to specified them, like 大舅 for the oldest brother of you mother, the following are 二舅, 三舅... For 叔叔 伯伯 they apply the same, just no 大叔, and the numbering should inherit from 伯s. There also have a word 大叔, but it's just a term to refer to some random older man...

For 叔叔, 伯伯 they can also refer to your parents' friends of their generation or your friends parents who are of same generation of your parents. Usually you won't use the term 舅舅 for this kind of acquaintances, but it happens when the guy is your mother's distance relatives, they might come from a same village with a same family name.

EDIT: 叔叔 is also used as a term of address for men (unrelated to you) who are roughly your father's age.