adjective
a word that describes or modifies a noun or pronoun, in this case, 'studious' describes someone who is diligent and hardworking in their studies
The studious student spent hours in the library conducting research for his thesis.
She's always been the studious type, never missing a class or assignment.
Dude, you're so studious, always hitting the books and acing your exams.
His mind was a studious sponge, absorbing every detail of the lecture.