detachment vs severance

detachment and severance both are nouns.

Word	Noun	Adjective	Verb	Adverb
detachment	Yes	No	No	No
severance	Yes	No	No	No

As nouns, severance is a hyponym of detachment; that is, severance is a word with a more specific, narrower meaning than detachment:

Other hyponyms of detachment include breach, break, falling out, rift, rupture, break.

detachment (noun)	severance (noun)
the act of releasing from an attachment or connection	the act of severing
coming apart	a personal or social separation (as between opposing factions)
avoiding emotional involvement
a small unit of troops of special composition
the state of being isolated or detached