fundamental

Synonyms: axiological axiomatic basal bottom bottom-line cardinal central constitutional constitutive crucial elemental elementary essential first foundational grass-roots indispensable integral intrinsic key major meat-and-potatoes necessary organic original paramount primary prime primitive primordial principal radical requisite rudimentary significant structural substratal substrative supporting sustaining theoretical underived underlying vital

Antonyms: additional advanced auxiliary extra minor secondary subordinate trivial unimportant

Synonyms: abcs axiom basis bottom line brass tacks coal and ice component constituent cornerstone element factor foundation guts heart law nitty-gritty principium principle rock bottom rudiment rule sine qua non theorem

Antonyms: addition auxiliary extra subordinate trivia