When hair thins is it also a matter of follicles producing fewer strands?

[Selb]

So rather than two or three strands like normal it becomes one strand coming out of the follicle? Like in my case I feel I don’t have any bald areas, but my hair is thinner in general, with more parting in between sections of my hair. I also have patchier areas being thinner. Same with the sides of my head.