I guess it depends on the specific context, but in general -
Fibrosis refers to a scarring process via connective tissue deposition. I typically associate this with inflammation
Sclerosis is "hardening" or "roughening" of a structure. +/- inflammation
Hyalinization refers to homogeneous deposition of nonspecific material (typically ECM protein/junk) characterized by a pink appearance on H&E. Usually not inflammatory
I am no pathologist, so maybe these have more specific histologic definitions that i am unaware of
