what’s up 禮貌嗎？

Is it polite to say 'What's up'?

The phrase 'what's up' can be seen as casual and friendly, but its politeness can depend on the context and the relationship between the people communicating. In some situations, it might come off as informal or too laid-back, while in others, it can be perfectly acceptable. Always consider the tone of the conversation and the individuals involved.