"How are you?"
Translation:तुम कैसे हो?
Why we are using here kaise instead of kaisa? Thought Kaise is used for plural? Can you please clarify?
Kaise is used for both plural and respectful forms. So it's aap kaise hain, aap kaise ho, tum kaise ho, tu kaisa hai, in descending levels of formality. Kaise is also used for plural, as in ve kaise hain, making the singular vah kaisa hai. (As a side note, don't use tu to refer to anyone except your closest friends, it's rude otherwise)