A main or major principle, rule, law, etc. which serves as the foundation or basis of a system; an essential part
The lowest frequency of a periodic waveform.
The lowest partial of a complex tone.
Related to a foundation. base, or basis; serving as a foundation.
essential; extremely important
Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment.
An operative person or thing.
That operates to produce an effect.