Formal:
* विषय (vishya) - This is the most common and formal way to say "topic."
* प्रकरण (prakaran) - This word is also used in formal settings and means "subject matter."
Informal:
* मुद्दा (mudda) - This is a more casual way to say "topic" and is commonly used in everyday conversations.
* बात (baat) - This word means "thing" or "matter" and can be used to refer to a topic.
* विषय वस्तु (vishya vastu) - This translates literally to "subject matter" and is less common than the other options.
The best word to use will depend on the specific context of your conversation. For example, if you are discussing a serious topic, you would likely use "विषय" or "प्रकरण." But if you are talking about something more casual, you could use "मुद्दा" or "बात."