Noun

• S: (n) fundamental (any factor that could be considered important to the understanding of a particular business) "fundamentals include a company's growth, revenues, earnings, management, and capital structure"
• S: (n) fundamental, fundamental frequency, first harmonic (the lowest tone of a harmonic series)

Adjective

• S: (adj) cardinal, central, fundamental, key, primal (serving as an essential component) "a cardinal rule"; "the central cause of the problem"; "an example that was fundamental to the argument"; "computers are fundamental to modern industrial structure"
• S: (adj) fundamental, rudimentary, underlying (being or involving basic facts or principles) "the fundamental laws of the universe"; "a fundamental incompatibility between them"; "these rudimentary truths"; "underlying principles"
• S: (adj) fundamental, profound (far-reaching and thoroughgoing in effect especially on the nature of something) "the fundamental revolution in human values that has occurred"; "the book underwent fundamental changes"; "committed the fundamental error of confusing spending with extravagance"; "profound social changes"