Correct term for having lost (not cut) one's hair
Is bald more correct than hairless when referring to someone who has lost their hair? Dictionary.com states that bald means
- having little or no hair on the scalp
and that hairless means
- without hair, bald
Both terms imply that a person has lost their hair or has just cut it.
Is there an unambiguous term that specifically means having lost one's hair in the sense that it will not grow anymore?
You are quite correct that simply describing someone simply as bald is ambiguous: it could mean that they can no longer grow hair, or that they have cut off all their hair.
To disambiguate:
Gone bald describes someone who has lost the ability to grow hair.
(Closely related, balding or going bald describes someone who is in the process of losing their ability to grow hair; either their hair is thinly distributed, or they have a (presumably small, but definitely increasing in size) bald patch.)
Shaved describes someone who has cut off their hair. (You'll generally want to specify what part of them has been shaved; saying "John has shaved" is not the same as saying "John has shaved his head".)
A reputable medical website http://webmd.com describes the condition alopecia as the medical term for baldness.
Notwithstanding a variety of treatments, cosmetics and quackery, the condition is more or less permanent.
Hairless, on the other hand, could be the result of a mechanical, not a bioogical process, and can usually be remedied by time and follicular activity.
Honestly, I think that "hairless" is also too ambiguous. It could mean that it never had hair to begin with.
I'd go with "gone bald." If you just say "bald" it could be temporary, but "gone bald" has a strong implication that it's more or less permanent.