Formal:
* धन्यवाद (Dhanyavaad) - This is the most common and formal way to say "thank you."
Informal:
* शुक्रिया (Shukriya) - This is a more informal and casual way to say "thank you."
* आभार (Aabhaar) - This is a slightly more formal way to express gratitude.
Other options:
* बहुत धन्यवाद (Bahut Dhanyavaad) - This means "thank you very much."
* आपका बहुत-बहुत धन्यवाद (Aapka bahut-bahut dhanyavaad) - This means "thank you very much" and is more polite.
The best way to choose the appropriate word depends on the situation and your relationship with the person you're speaking to.