What does costa mean?
Costa is a formal, technical term meaning a rib or any riblike structural feature. In anatomy it denotes one of the ribs of the vertebrate skeleton; in botany it can refer to the midrib or principal vein of a leaf or frond; in entomology it names the thickened vein along the leading edge of an insect's wing; and in conchology it describes a ribbed ridge on certain shells. Because these senses all share the underlying idea of a rib-shaped support or ridge, the word travels comfortably across biological disciplines. Derived forms such as 'costal' (relating to the ribs) and the plural 'costae' appear regularly in scientific literature. Though rarely used in casual speech, where 'rib' serves perfectly well, costa is valuable for precise description, and its Latin root also gave English the everyday words 'coast' and 'intercostal'.
nounA rib or a riblike anatomical structure; in biology, specifically a rib, a main vein or rib of a leaf or insect wing, or a ridge on a shell.
- Anatomy: a rib.
- Biology generally: a riblike structure, such as the midrib of a leaf, the thickened front vein of an insect's wing, or a longitudinal ridge on certain shells.
"The surgeon carefully traced each costa during the thoracic examination."
"The radiograph showed a fracture in the eighth costa."
"Under magnification, a prominent costa runs along the leading edge of the moth's wing."
Standard plural follows the Latin pattern; occasionally anglicized as 'costas' in informal scientific writing, but 'costae' is preferred in formal usage.
"The dissection revealed twelve pairs of costae."
The English word 'coast' began life as the Latin word for your ribs — because a map's edge hugs a country like a rib cage.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of costa
Costa comes directly from Latin costa, meaning 'rib' or 'side'. English adopted it as a learned borrowing, so it appears chiefly in scientific registers. The same Latin root produced 'costal' and 'intercostal' (between the ribs), and through Vulgar Latin it developed into Old French 'coste', giving English 'coast' — originally the 'side' or 'rib' of a country, later narrowed to its seashore. The plural is the Latin-form 'costae'.
Related word forms
How costa is actually used
Strictly technical vocabulary, found mainly in anatomy, botany, entomology, and conchology rather than everyday speech. In ordinary conversation English speakers say simply 'rib'. The plural is the Latinate 'costae', though informal scientific writing sometimes uses 'costas'.
Easily confused with costa
A 'coast' is land beside the sea (from the same Latin root costa), while 'costa' is the technical term for a rib or riblike structure.