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.
Tips
- Slow down to greet someone you know. You don't have to stop what you are doing (walking, working, shopping).
- Say an appropriate form of hello.
- Smile and wave.
Useful phrases
Listen and read:
- 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.
** Native speakers often shorten going to goin' in casual speech.
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".
Listen and read:
- Howdy
- Hiya
- Whazzup?
- Yo
- G'day (Australia)