something that you say or do to greet sb
She waved a friendly greeting.
They exchanged greetings and sat down to lunch.
He raised his hand in greeting .
a message of good wishes for sb's health, happiness, etc.
Christmas/birthday, etc. greetings
My mother sends her greetings to you all.
used at Christmas to wish sb an enjoyable holiday
Hello is the most usual word and is used in all situations, including answering the telephone.
Hi is more informal and is now very common.
How are you? 或 How are you doing? （非常口语化）常用于Hello和Hi之后：
How are you? or How are you doing? (very informal) often follow Hello and Hi .
‘Hello, Mark.’ ‘Oh, hi, Kathy! How are you?’
Good morning is often used by members of a family or people who work together when they see each other for the first time in the day. It can also be used in formal situations and on the telephone. In informal speech, people may just say Morning .
Good afternoon和Good evening少用得多。Good night只在晚上说再见或上床睡觉前说，不用以打招呼。
Good afternoon and Good evening are much less common. Good night is not used to greet somebody, but only to say goodbye late in the evening or when you are going to bed.
第一次与人见面时可说Pleased to meet you或Nice to meet you（较非正式）。在正式场合有些人用How do you do? ，正确的回答是How do you do?
If you are meeting someone for the first time, you can say Pleased to meet you or Nice to meet you (less formal). Some people use How do you do? in formal situations. The correct reply to this is How do you do?