Formal:
* 알아요 (alayyo): This is the most common and polite way to say "I know". It's used when speaking to someone older or someone you want to be respectful to.
Informal:
* 알아 (ara): This is a more casual way to say "I know" and is used when speaking to friends or family.
* 아는데 (ande): This is similar to "ara" but adds a nuance of "I know that" or "I know it".
Other expressions:
* 잘 알아요 (jal alayyo): This translates to "I know well" and emphasizes that you have a good understanding of something.
* 모르겠어요 (moreugeseyo): This means "I don't know" and is the opposite of "I know."
Example:
* "저는 그 영화를 알아요." (Jeoneun geu yeonghwareul alayyo.) - "I know that movie." (Formal)
* "나 그거 알아." (Na geugeo ara.) - "I know that." (Informal)
The best way to use these phrases is to consider the context and your relationship with the person you are speaking to.