For a male nephew:
* சொந்த மகன் (sontha makan): This is the most common and general term for nephew. It literally means "own son," but it's used for a brother's son.
* சகோதரன் மகன் (sakodharan makan): This is more literal, meaning "brother's son."
* அண்ணன் மகன் (annan makan): This means "elder brother's son."
* தம்பி மகன் (thampi makan): This means "younger brother's son."
For a female nephew:
* சொந்த மகள் (sontha makal): This is the general term for niece, meaning "own daughter."
* சகோதரன் மகள் (sakodharan makal): This means "brother's daughter."
* அண்ணன் மகள் (annan makal): This means "elder brother's daughter."
* தம்பி மகள் (thampi makal): This means "younger brother's daughter."
The choice of term depends on the specific context and the speaker's relationship to the nephew/niece.