noun

1. (usually in the plural) A leading or primary principle, rule, law, or article, which serves as the groundwork of a system; an essential part

   “one of the fundamentals of linear algebra”

2. The lowest frequency of a periodic waveform.

3. The lowest partial of a complex tone.

adjective

1. Pertaining to the foundation or basis; serving for the foundation.

2. Essential, as an element, principle, or law; important; original; elementary.

   “A need for belonging seems fundamental to humans.”

Synonyms: groundlaying