subsistence vs bread and butter

subsistence and bread and butter both are nouns.

Word	Noun	Adjective	Verb	Adverb
subsistence	Yes	No	No	No
bread and butter	Yes	No	No	No

As nouns, bread and butter is a hypernym of subsistence; that is, bread and butter is a word with a broader meaning than subsistence:

Other hypernyms of subsistence include keep, livelihood, living, support, sustenance.

subsistence (noun)	bread and butter (noun)
minimal (or marginal) resources for subsisting	the financial means whereby one lives
the state of existing in reality; having substance
a means of surviving