thorough

Thorough means doing something very carefully and making sure everything is done completely. For example, when you clean your room, you need to be thorough. That means you clean every part of your room, like the floor, the bed, and the toys. You don't leave anything dirty or messy.

Thorough can also mean knowing a lot about something. For example, if you are a thorough reader, it means you read a lot of books and know many stories and facts.