What does abomasus mean?
An abomasus is the fourth and final chamber of the four-part stomach found in ruminants such as cattle, sheep, goats, and deer. While the first three chambers — the rumen, reticulum, and omasum — handle fermentation, regurgitation of cud, and water absorption respectively, the abomasus performs true glandular digestion: it secretes hydrochloric acid and enzymes such as pepsin to break down food chemically, much as the human stomach does. For this reason it is sometimes called the 'true stomach'. The word derives from New Latin and is closely associated with the term abomasum, which has largely displaced it in contemporary veterinary literature. It appears almost exclusively in technical contexts, particularly discussions of livestock health, where conditions like displaced abomasus are significant concerns in dairy farming.
nounThe fourth and most muscular chamber of the stomach of a ruminant, in which digestion is completed by gastric juices; more commonly known in English by its New Latin form 'abomasum'.
- The fourth, glandular compartment of the ruminant stomach, equivalent to the simple human stomach.
"The veterinarian explained that the calf's illness stemmed from an abnormality in its abomasus."
"Displaced abomasus is one of the most common digestive disorders seen in dairy cattle after calving."
"In comparative anatomy classes, students learn that the abomasus secretes hydrochloric acid and pepsin just like a monogastric stomach."
The Latinate plural 'abomasa' is standard in technical writing; the anglicized 'abomasuses' also occurs but is less common.
"The study compared the acidity of the abomasa across several breeds of sheep."
Cows chew their cud through three stomachs before food ever reaches the abomasus — the only one that digests like our own.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of abomasus
The word comes from New Latin, formed from the Latin prefix 'ab-' (meaning 'away from') combined with 'omasus', itself borrowed from the name of the third stomach chamber, the omasum. The prefix reflects the fact that the abomasus lies beyond, or further along from, the omasum in the digestive tract. The closely related form 'abomasum' arose in the same scientific tradition and remains the standard term in English-language veterinary and anatomical writing today, with 'abomasus' surviving mainly as a variant.
How abomasus is actually used
'Abomasus' is a rare Latinate variant; modern veterinary and scientific writing overwhelmingly prefers the form 'abomasum' (plural 'abomasa'). The word belongs to formal, technical registers — zoology, veterinary medicine, and comparative anatomy — and would sound out of place in everyday speech.
Easily confused with abomasus
The omasum is the third chamber of a ruminant's stomach, concerned chiefly with water absorption, whereas the abomasus (or abomasum) is the fourth chamber, where acid-and-enzyme digestion takes place.