fundamental in WordNet English dictionary

1. 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"
   cardinal  central  fundamental  key  primal 
   
2. being or involving basic facts or principles
   "the fundamental laws of the universe"; "a fundamental incomatibility between them"; "these rudimentary truths"; "underlying principles"
   fundamental  rudimentary  underlying 
   
3. 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"
   fundamental  profound 
   

1. the lowest tone of a harmonic series
   fundamental  fundamental frequency  first harmonic 
   
2. 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"
   fundamental