Obsolescence is a synonym of obsoleteness.
As nouns the difference between obsoleteness and obsolescence
is that obsoleteness is quality or state of being obsolete or unused while obsolescence is the state of being obsolete—no longer in use; gone into disuse; disused or neglected.
obsoleteness
English
Noun
(-)
Quality or state of being obsolete or unused.
Synonyms
* obsolescence (much more common)
obsolescence
Noun
(uncountable) The state of being obsolete—no longer in use; gone into disuse; disused or neglected.
*
(countable) The process of becoming obsolete, outmoded or out of date.
* '>citation
Synonyms
* obsoleteness (much less common)
* obsoletion
Derived terms
* planned obsolescence
Related terms
* expiration
* expiry
* life span
* obsolescent
* obsolete
* shelf life