Fundamental

[fuhn-duh-men-tl] /ˌfʌn dəˈmɛn tl/

adjective
1.
serving as, or being an essential part of, a foundation or basis; basic; underlying:
fundamental principles; the fundamental structure.
2.
of, relating to, or affecting the foundation or basis:
a fundamental revision.
3.
being an original or primary source:
a fundamental idea.
4.
Music. (of a chord) having its root as its lowest note.
noun
5.
a basic principle, rule, law, or the like, that serves as the groundwork of a system; essential part:
to master the fundamentals of a trade.
6.
Also called fundamental note, fundamental tone. Music.

7.
Physics. the component of lowest frequency in a composite wave.
/ˌfʌndəˈmɛntəl/
adjective
1.
of, involving, or comprising a foundation; basic
2.
of, involving, or comprising a source; primary
3.
(music) denoting or relating to the principal or lowest note of a harmonic series
4.
of or concerned with the component of lowest frequency in a complex vibration
noun
5.
a principle, law, etc, that serves as the basis of an idea or system
6.

7.
(physics) Also called fundamental frequency, first harmonic

adj.

mid-15c., “primary, original, pertaining to a foundation,” modeled on Late Latin fundamentalis “of the foundation,” from Latin fundamentum “foundation” (see fundament). Fundamentals “primary principles or rules” of anything is from 1630s.