I sometimes write sentences like this:
To prove the desired result, the following notions will be handy.
What follows is a usually a sequence of definitions, theorems and proofs. Therefore, I don't think that the word 'notions' really fits, because 'theorems' aren't really 'notions' to my mind.
Question. Is there a word that does fit, which encompasses both definitions and theorems?
"Theory" is theoretically the answer :) Otherwise, settings/framework?