informal (friends & family)
1. Hey, how's it going?
2. What's up?
3. What's happening? *
4. Hey dude, what's happening? *(The word "dude" is very popular among friends.)
5. Hey, you guys. How's it going? (When addressing a large group of people you know, "you guys" is very common--even among women)
6. Hey, bro. 'Sup. (The word "bro" is short for brother. This is popular among African Americans, but it has also been adopted by the wider public. The slang word "sup" is a contraction of "what's up?" )
Note: The "g" sound at the end of words is often dropped in informal speech.
formal (polite & in the office)
1. Hi. How are you?
2. Hello! How are you today?
3. Good morning. / Morning.
4. Good afternoon.
5. Good evening.
Meeting someone for the first time
1. How do you do? (formal)
2. I'm happy to make your acquaintance. (very formal)
3. It's a pleasure to meet you. (Less formal, but use this with someone you admire or someone who know about but have never met.)
4. I'm pleased to meet you.
5. It's nice to meet you.
6. Nice to meet you.
7. Hey, how's it going? (informal)