atardecer
/ataɾdeˈθeɾ/ · B2 · verb
late afternoon, sunset, dusk, evenfall, nightfall
🌇 a- + tarde (late afternoon) + -ecer (to become) = to become late afternoon
Atardecer is built from tarde, meaning late or afternoon, plus the verb ending -ecer, meaning to become or grow. So it literally means to grow late in the day. As a noun, it names the dusk that results.