fundamental

Etymology

From Late Latin fundamentālis, from Latin fundamentum (“foundation”), from fundō (“to lay the foundation (of something), to found”), from fundus (“bottom”), from Proto-Indo-European *bʰudʰmḗn.

noun

1. (usually in the plural) A main or major principle, rule, law, etc. which serves as the foundation or basis of a system; an essential part
   one of the fundamentals of linear algebra
   When any one offers me a compleat Catalogue of his Fundamentals, he does not unreaſonably demand me to quit mine for nothing[…] 1722, John Locke, The Works of John Locke ...: With Alphabetical Tables ..., page 572
   Personal leadership is a fundamental of successful government. 1928, Franklin D. Roosevelt, The Happy Warrior Alfred E. Smith, Houghton Mifflin, →OCLC, →OL, page 28
2. (physics) The lowest frequency of a periodic waveform.
3. (music) The lowest partial of a complex tone.

adj

1. Related to a foundation. base, or basis; serving as a foundation.
2. Essential; extremely important.
   a fundamental truth; a fundamental axiom; a fundamental element; fundamental principle; fundamental law
   A need for belonging seems fundamental to humans.
   Seeing the British establishment struggle with the financial sector is like watching an alcoholic […]. Until 2008 there was denial over what finance had become. […] But the scandals kept coming, […]. A broad section of the political class now recognises the need for change but remains unable to see the necessity of a fundamental overhaul. Instead it offers fixes and patches. 2013-06-28, Joris Luyendijk, “Our banks are out of control”, in The Guardian Weekly, volume 189, number 3, page 21