Synonyms for Fundamental:

adj.

all (adjective)
profound.
bottom (adjective)
elementary, bottom, basic, foundational, underlying, lowest, base.
capital (adjective)
basic, important.
component (adjective)
elemental.
critical (adjective)
crucial.
deep-rooted (adjective)
ingrained.
fundamental (adjective)
key, primary, requisite, basal, cardinal, essential, intrinsic, theoretical, supporting, prime, vital, major, necessary, structural, rudimentary, central, elementary, underlying, foundational, crucial, first, principal, bottom, significant, integral, axiomatic, constitutive, elemental.
important (adjective)
meaningful, serious.
intrinsic (adjective)
implicit, inherent, intrinsic, component, deep down, elemental, central, built-in, inwoven, inseparable, integral, ingrained, unalienable.
pure (adjective)
aboriginal, stark, faultless, decent, honorable, nascent, unsullied, bare, basic, essential, elemental, unalloyed, elementary, plain, undiluted, formative, sinless, stainless, clean, simple, primal, purebred, angelic, irreducible, pure, untainted, unadulterated, white, guiltless, atomic, clear, foundational, blameless, monolithic, spotless, unblemished, indivisible, virtuous, Simon-pure, basal, chaste, primary, innocent, untarnished, unadorned, immaculate, undefiled, uncluttered, prime, austere.
severe (adjective)
imperial, spartan, harsh, acute, rigid, grim, dry, correct, brisk, disciplined, acerbic, exacting, rigorous, demanding, stark, censorious, hidebound, ascetic, oppressive, authoritarian, piquant, cool, caustic, strict, stern, keen, lean, intense, bleak, relentless, frosty, meticulous, uncompromising, chilly, stringent, stiff-necked, crisp, puritanical, curt, brusque, austere, unbending, sharp, precise, obdurate, raw, blunt, acrimonious, astringent, strait-laced, draconian, abrupt, short, critical, obstinate, basic, inflexible, spare, intolerant, cutting, severe, dour, icy, tart, gruff, prudish.
united (adjective)
atomic, undivided, coincident, congruous, coherent, same, indivisible, united, unified, homogeneous, congruent, entire, holistic, irreducible, integrated, intact, monolithic, integral, pure, cohesive, single, elemental, simple, solid, uniform, complete.

n.

surface. ultimate. be, constitutive. base (noun)
core.
basis (noun)
base.
essential (noun)
necessary, requisite.
fundamental (noun)
basic, underlying, significant, primal, first harmonic, fundamental frequency, profound, important, of import, component, rudimentary, key, cardinal, central.

Other synonyms:

constitutive. ultimate, vital. core. essential
necessary.

Usage examples for fundamental

  1. The superiority of the pleasures of intellect to those of sense, Mr Godwin considers as a fundamental truth. – An Essay on the Principle of Population by Thomas Malthus
  2. Susan safe- guarded her wandering fancies as sternly as she did herself, would as quickly have let Peter, or any other man, kiss her, as to have dreamed of the fundamental and essential elements of marriage. – Saturday's Child by Kathleen Norris
  3. As in the fundamental passage, so here also, the sceptre, the symbol of dominion, stands for dominion itself. – Christology of the Old Testament: And a Commentary on the Messianic Predictions, v. 1 by Ernst Wilhelm Hengstenberg