Alveolus (/ælˈviːələs/ al-VEE-ə-ləs, UK also /ˌælviˈoʊləs/ AL-vee-OH-ləs; pl. alveoli /ælˈviːəlaɪ/ al-VEE-ə-ly, UK also /ˌælviˈoʊlaɪ/ AL-vee-OH-ly; from Latin alveolus 'little cavity') is a general anatomical term for a concave cavity or pit.