fundamental

[1]	fundamental frequency , principle , law , first harmonic , rule , axiom , essential , element , cornerstone , keystone

adj.

[1]	basic , rudimentary , elementary , primary , main , prime , first , principal , underlying , cardinal , central , essential , quintessential , constitutional , inherent , intrinsic , important , crucial , critical , organic , vital
[2]	cardinal , central , key , primal
[3]	rudimentary , underlying
[4]	profound