housing vs casing

housing and casing both are nouns.

Word	Noun	Adjective	Verb	Adverb
housing	Yes	No	No	No
casing	Yes	No	No	No

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

housing: a protective cover designed to contain or support a mechanical component
casing: the housing or outer covering of something

housing (noun)	casing (noun)
structures collectively in which people are housed	the enclosing frame around a door or window opening
a protective cover designed to contain or support a mechanical component	the housing or outer covering of something
stable gear consisting of a decorated covering for a horse, especially (formerly) for a warhorse	the outermost covering of a pneumatic tire