What does alveolus mean?
An alveolus is a small hollow or cavity, but the word is best known for two specific structures in human anatomy. In the lungs, each alveolus is one of hundreds of millions of microscopic, thin-walled air sacs clustered at the ends of the bronchioles; it is here that oxygen passes from inhaled air into the bloodstream while carbon dioxide moves out to be exhaled. In dentistry, an alveolus refers to the bony socket in the upper or lower jaw that anchors a tooth. The word is strictly technical, appearing in anatomy textbooks, medical literature, and dental practice rather than casual speech, and it is nearly always encountered in its plural form, alveoli, since these structures exist only in vast numbers. Derived from Latin, it carries connotations of precision and clinical expertise, making it essential vocabulary for students of medicine, biology, and dentistry alike.
nounA small cavity or pit, especially one of the tiny air sacs in the lungs where gas exchange with the blood takes place, or the socket in the jawbone that anchors a tooth.
- One of the tiny thin-walled air sacs at the end of the bronchioles in the lungs, where oxygen and carbon dioxide are exchanged with the blood.
- The bony socket in the jaw (the dental alveolus) that holds the root of a tooth.
"Each alveolus in the lung is wrapped in a fine mesh of capillaries, allowing oxygen to pass into the blood."
"Damage to a single alveolus is invisible, but widespread destruction of these sacs is what defines emphysema."
"After the tooth was extracted, the empty alveolus gradually filled with new bone over several months."
The plural follows the standard Latin pattern (-us → -i). The plural is considerably more common than the singular in both pulmonary and dental usage.
"Smoking progressively destroys the delicate walls of the alveoli, reducing the lung's capacity for gas exchange."
Your lungs contain roughly 300 million of these microscopic sacs — if you flattened them all out, they would cover a tennis court's worth of surface area packed inside your chest.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of alveolus
Alveolus comes directly from Latin, where it meant a small hollow, cavity, or belly — literally a diminutive related to 'alvus' (belly, womb). It entered English in the early modern period as anatomists adopted Latin terminology to describe small cavities in the body. The same Latin root gives us the adjective 'alveolar' and related terms such as 'alveolate', meaning pitted or honeycombed like the structure of lung tissue itself.
Related word forms
How alveolus is actually used
Alveolus is a technical term used almost exclusively in medical, anatomical, and dental contexts; it rarely appears in everyday conversation. The plural 'alveoli' is far more common than the singular in medical writing, since these structures are always discussed in large numbers. In dentistry, 'dental alveolus' or 'tooth socket' may be used interchangeably.
Easily confused with alveolus
Alveolus is the noun naming the cavity or air sac itself, while alveolar is an adjective describing something relating to or situated in those structures.
Alveole is a rare variant spelling of the same word; alveolus is the standard form in modern English.