The basis of something.
A stone laid during the construction of a (usually important) building, the laying of which is usually marked by a ceremony.
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