Greetings in Passing
It is polite to greet a person you know. However, you don't always have time to stop and have a conversation. Just remember to smile as you say hello. A small wave is also polite. Sometimes you pass the same person a second time on the same day. You can say "hello again" or just smile.
跟认识的人打招呼是有礼貌的体现，但是你们并不会每次都有时间停下来谈谈。只要记住说“你好”的时候带上微笑就行了，另外轻轻招手也会显得很礼貌。有些时候你可能在同一天再次碰到这个人，那时你可以说"hello again"，或者仅用微笑示意。
Tips
•Slow down to greet someone you know. You don't have to stop what you are doing (walking, working, shopping).
放慢动作来同认识的人打招呼，不必停下（脚步，工作，购物）。
•Say an appropriate form of hello.
选择正确的打招呼方式。
•Smile and wave.
微笑+挥手。
Useful phrases
•Hello
•Hi
•Good morning
•Good afternoon
•Good evening*
•Hey, John.
•How's it goin'?**
*Good night is a farewell (goodbye) phrase. It is NOT a greeting to use at night time.
"Good night."是用来告别（再见）的短语，并不是晚间打招呼的说法。
**Native speakers often shorten "going" to "goin" in casual greetings.
母语者在比较随意地问候时经常将"going"缩略说成"goin"。
Slang greetings in passing
Using slang in a greeting is typical between close friends. Teens often use slang when they greet each other. Certain English speaking countries also have their own popular form of "hello".
用俚语来打招呼经常发生在好朋友间，年轻人见面时常用俚语互相致意，而每个英语国家也有自己所流行的问候方式。
•Howdy
•Hiya
•Whazzup?
•Yo
•G'day (Australia)
