If you are studious, you study a lot and you probably even enjoy it. Your studious habits might bring you excellent grades and "your" table at the library.
You can see study in studious. Remember, being smart doesn't make you studious — unless you also hit the books. That's why studious people are sometimes also called bookish. Studious can also describe doing something carefully, with effort. If you are studious in your approach to baking, you read the recipe over and over, double-checked that you have all the ingredients and measure them down to the exact drop.