What are the rules for when to use what vs. which?

Answer by  HelpChat (494)

What is used to describe a single object or category. Which is used to identify that there is a group of objects or multiple categories within a main subject. For example: I know where I want to eat, but I don't know which sandwich I'll order.

Answer by  cathybellejones (309)

The word "what" is a more general term than the word "which". The example of "what" would be like saying "What restaurant serves seafood?" Whereas the word "which" is a more direct comparative. Example: "Which restaurant serves better seafood, Fishy Joe's or Shrimp World?"