The adjective is indivisible.
Invisible
Something that cannot be divided any further.a tomes means : Volume A
Something that cannot be divided any further.a tomes means : Volume A
To recover something, or to retrieve it.
Deaf
Alternate. substitute (verb)
It means to replace something, with something else that is equivalent.
The likely word sought is substitute (something used in the place of something else, or an alternate player in sports).
atom
The word substitute can be a verb and a noun. The verb form means to use something in place of something else. The noun form is a replacement for something which does a similar thing.
something that cannot be avoided = inevitable
The words for unable to be fixed are uncorrectable, irremediable, irreparable, or incurable.The word for unable to be "corrected" (as in made to conform) is incorrigible.