Formal:
* क्या आप हैं? (Kya aap hain?) - This is the most formal way to say "are you?" and is used when addressing someone you don't know well or someone older or in a position of authority.
Informal:
* क्या तुम हो? (Kya tum ho?) - This is a more informal way to say "are you?" and is used when talking to friends, family, or someone younger than you.
* तुम हो? (Tum ho?) - This is even more informal and can be used with close friends or family. It literally translates to "you are?", but it implies "are you?" in the context of a conversation.
For a question asking if someone is present:
* क्या आप यहां हैं? (Kya aap yahaan hain?) - This means "Are you here?" and is used to check if someone is present.
It's important to use the appropriate level of formality when speaking Hindi. Using the wrong form can be considered rude or disrespectful.