eternamente
/eˌteɾnaˈmente/ · B2 · adv
eternally
♾️ eterna + mente = eternal + manner, so 'in an eternal way'
Eternamente is built from eterna (eternal, feminine form) plus the adverb suffix -mente, which works like English -ly. Read it as eternal + -ly: doing something in an endless way. Same -mente ending as in rápidamente and felizmente.