2. The most common greeting in English is "Hello".
Saying hello is correct for both formal and informal situations.

3. "Hi" is less formal than hello.
Saying hi can be used in both formal and informal
settings, but it is always safer to say hello if you're not
sure which greeting to use.

4. "Howdy" is an informal greeting.
It is a popular way to greet someone in southern and western
states, especially in Texas.

5. "What's up?" is American slang. It is a very informal way to greet
someone.
What's up? is a popular greeting among young people and
people who know each other very well.

6. "How's it going?" is an informal greeting. It is a casual and
friendly way to greet someone.
People who ask this question are usually trying to start a
conversation.

7. "Good morning" is both a formal and informal greeting.
Co-workers often greet each other by saying good morning.
Americans say good morning from sunrise to noon.

8. "Good afternoon" is both a formal and informal greeting.
You can say good afternoon to both strangers and friends.
Americans say good afternoon from noon until about 5:00 PM.

9. "Good evening" is both a formal and informal greeting.
You can say this to both strangers and friends.
Americans say good evening from about 5:00 PM until sunrise.
After sunrise, they say good morning.