plasticiser vs softener

plasticiser and softener both are nouns.

Word	Noun	Adjective	Verb	Adverb
plasticiser	Yes	No	No	No
softener	Yes	No	No	No

As nouns, softener is a hypernym of plasticiser; that is, softener is a word with a broader meaning than plasticiser:

plasticiser: a substance added to plastics or other materials to make them more pliable
softener: a substance added to another to make it less hard

plasticiser (noun)	softener (noun)
a substance added to plastics or other materials to make them more pliable	a substance added to another to make it less hard