Formal:
* 안녕하십니까? (Annyeonghaseumnikka?) - This is the most formal and respectful way to greet someone in the morning. It's used when addressing someone much older than you, a superior, or someone you don't know well.
Informal:
* 안녕하세요 (Annyeonghaseyo) - This is the most common and widely used greeting, suitable for friends, family, and people your age. It's also used when talking to someone older than you in a casual setting.
* 좋은 아침입니다 (Joheun achimimnida) - This literally translates to "It's a good morning," and is a more direct way to say "good morning." It's more formal than "안녕하세요" but less formal than "안녕하십니까?"
Even more casual:
* 굿모닝 (Good morning) - This is an English loanword that is commonly used in informal situations.
The best way to choose the right greeting is to consider the context and the relationship you have with the person you're talking to.