你好 (nǐ hǎo)
This is a general greeting that can be used in most situations.
There are also other ways to say "Hello" depending on the context and level of formality:
* 您好 (nín hǎo): More formal, used when addressing someone older or of higher status.
* 早上好 (zǎoshang hǎo): Good morning.
* 下午好 (xiàwǔ hǎo): Good afternoon.
* 晚上好 (wǎnshang hǎo): Good evening.
* 嗨 (hāi): Informal, used with friends or close acquaintances.