fundamental/a. amp; n. lME. adj. 1 Of or pertaining to the basis or groundwork; going to the root of the matter. 2 Serving as the base or foundation; essential or indispensable. Also, primary, original; from which others are derived. 3 Of or pertaining to the foundation(s) of a building. 4 Of a stratum: lowest, lying at the bottom.
Fundamentalismn. E20 [f. prec. + -ISM.] The strict maintenance of traditional orthodox religious beliefs or doctrines; esp. belief in the inerrancy of religious texts.
– The New Shorter Oxford English Dictionary
You must remember this, a kiss is still a kiss,
A sigh is just a sigh;
The fundamental things apply,
As time goes by.
– Herman Hupfeld, ‘As Time Goes By’ (1931 song)