* Her studiousness was evident in the way she meticulously highlighted her textbooks.
* Despite his young age, the boy's studiousness impressed his teachers.
* The library was a haven for studiousness, with students quietly absorbed in their books.
* The professor praised the student's studiousness and dedication to her studies.
* His studiousness paid off, as he graduated with honors.
You can also use "studiousness" in more figurative ways:
* Her studiousness in the kitchen led to her becoming an award-winning chef.
* The detective's studiousness in examining the evidence was crucial in solving the crime.