fundamental(pertaining to the foundation or basis; serving for the foundation) adjective [UK: ˌfʌn.də.ˈmen.tl̩] [US: ˌfʌn.də.ˈmen.tl̩]
fundamenta interago noun
fundamental interaction(basic forces that act between elementary particles) noun [UK: ˌfʌn.də.ˈmen.tl̩ ˌɪn.tə.ˈræk.ʃn̩] [US: ˌfʌn.də.ˈmen.tl̩ ˌɪn.tə.ˈræk.ʃn̩]