alveolus

noun

al·​ve·​o·​lus al-ˈvē-ə-ləs 

plural alveoli al-ˈvē-ə-ˌlī 

-(ˌ)lē

1

: a small cavity or pit: such as

a

: a socket in the jaw for a tooth

b

: a small air-containing compartment of the lungs in which the bronchioles terminate and from which respiratory gases are exchanged with the pulmonary capillaries

c

: an acinus of a compound gland

d

: a cell of a honeycomb

2

: alveolar ridge sense 2

Examples of alveolus in a Sentence

Recent Examples on the Web

This balloon can, in turn, can push against the alveoli in the lung. — Bruce Y. Lee, Forbes.com, 20 Mar. 2026

The alveoli take in oxygen from inhaled air and exchange it for carbon dioxide, a waste gas that is exhaled. — Susan Russell, Verywell Health, 23 Dec. 2025

Her primary focus was on hyaline membrane disease, sometimes called respiratory distress syndrome, in which alveoli — tiny air sacs in the lungs — do not properly inflate. — Matt Schudel, Washington Post, 3 July 2024

Plateau pressure represents the pressure in the alveoli at some particular phase of breathing and is often used as a gauge to determine the maximum pressure that can be applied. — Ravinder Dahiya, IEEE Spectrum, 29 May 2020

Word History

Etymology

New Latin, from Latin, diminutive of alveus cavity, hollow, from alvus belly, beehive; akin to Lithuanian aulys beehive, Greek aulos tube, flute

First Known Use

1657, in the meaning defined at sense 1

Kids Definition

alveolus

noun

al·​ve·​o·​lus al-ˈvē-ə-ləs 

plural alveoli -ˌlī 

-(ˌ)lē

: a small cavity or pit

especially : an air cell of the lungs

Medical Definition

alveolus

noun

al·​ve·​o·​lus al-ˈvē-ə-ləs 

plural alveoli -ˌlī  -(ˌ)lē 

: a small cavity or pit: as

a

: a socket in the jaw for a tooth

b

: any of the small thin-walled air-containing compartments of the lung that are typically arranged in saclike clusters into which an alveolar duct terminates and from which respiratory gases are exchanged with the pulmonary capillaries

c

: an acinus of a compound gland

d

: any of the pits in the wall of the stomach into which the glands open