This is his study of the value in speaking well. [a detailed analysis of something]
Where is your study? Oh, it's by the front door. [the room in which you study]
His line of study is the interaction of allopathic drugs. [a piece of academic work]
studies: [studying or something involving study]
We will further our studies in the US
Balancing our studies and our social lives is hard but necessary.
It can also be used in titles of academic departments:
The Department of Metallurgical Studies
I don't think I have met "studying" used as a noun.
Student or Learner