What does costae mean?
Costae is the plural of the noun costa, a term borrowed from Latin meaning "rib" or "side." In human anatomy, the costae are the ribs — typically twelve pairs of curved bones arching from the spine toward the breastbone, enclosing and protecting the heart and lungs. The word also has important uses outside medicine: in botany, a costa is the central rib of a leaf or frond, especially in mosses and ferns, and in entomology it is the thickened front vein along the leading edge of an insect's wing. Because of these technical senses, costae belongs chiefly to formal scientific registers; ordinary speakers simply say "ribs." It carries no emotional connotation, but its precision makes it indispensable in anatomical description. Its relatives include costal (relating to the ribs), intercostal (between the ribs), and even coast, which shares the same Latin ancestor.
noun"Costae" is the plural of "costa," meaning ribs or rib-like structures; in anatomy it refers to the ribs of the body, while in botany and zoology it denotes various rib-shaped parts such as the midrib of a leaf, a vein of an insect wing, or a ridge on a shell.
- Anatomy: the ribs of the body (plural of costa).
- Botany/zology: rib-like structures such as the midrib of a fern frond or moss leaf, the main vein of an insect wing, or ridges on shells.
"The radiologist traced each of the twelve costae on the chest X-ray before confirming that no fracture was present."
"In humans there are normally twelve pairs of costae forming the thoracic cage."
"Under the microscope, each moss leaf shows a single prominent costa running down its centre."
"Costae" is itself the standard Latin plural of "costa"; singular forms use "costa," and adjectival forms include "costal" and "costate." In scientific writing it should be italicised if treated as a foreign term, though many style guides now accept roman type.
"A fracture of the lower left costae was visible on the CT scan."
The English word "coast" is literally the same word as "ribs" — both come from Latin costa — because early speakers pictured the shoreline as the 'ribs' of a country.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of costae
Costae comes directly from Latin costa, meaning "rib" or "flank." Latin adopted the word into medical vocabulary, and Renaissance anatomical writing carried it into English, where it became the standard technical term for the ribs. The same root produced costal and intercostal in anatomy and, by way of Old French, the English word "coast," originally meaning the side or border of a country.
Related word forms
How costae is actually used
"Costae" is a technical plural used almost exclusively in anatomy, botany, and zoology; in everyday speech people say "ribs." It is a learned Latinate plural, so it appears mainly in formal, scientific writing rather than conversation.
Easily confused with costae
"Coast" refers to land beside the sea and derives from the same Latin root as "costa," but it has nothing to do with ribs.
A hosta is a garden plant, whereas costae are ribs or rib-like structures.