Fundamental

Synonyms for fundamental
adj basic, important

major
paramount
integral
crucial
indispensable
constitutional
elemental
theoretical
underlying
necessary
vital

significant
radical
elementary
central
principal
intrinsic
essential
structural
prime
supporting
primitive

organic
bottom
primary
cardinal
key
requisite
original
first
axiomatic
basal
primordial

rudimentary
constitutive
axiological
bottom-line
foundational
grass-roots
meat-and-potatoes
substratal
substrative
sustaining
underived

Antonyms for fundamental

lesser
minor
insignificant
unimportant
least
trivial
extrinsic

unnecessary
inessential
needless
nonessential
learned
auxiliary
additional

advanced
extra
subordinate
secondary
accessory

Synonyms
noun basic, essential part

foundation
component
element
principle
factor
bottom line

law
cornerstone
heart
guts
rudiment
basis

nitty-gritty
rule
theorem
constituent
axiom
brass tacks

rock bottom
sine qua non
ABCs
coal and ice
principium

Antonyms

cowardice
fear
auxiliary

extra
subordinate
trivia

addition