What does costal mean?
Costal is an adjective meaning relating to the ribs or the sides of the body where the ribs lie. It comes from the Latin word 'costa', meaning rib. In medicine and anatomy it is a standard technical term, appearing in phrases like costal cartilage (the flexible tissue connecting each rib to the breastbone), costal margin (the lower edge of the rib cage at the front of the torso), and costal breathing (breathing driven by movement of the rib muscles). Zoologists also use the term for the leading edge of certain structures, notably the costal margin or costal vein along the front edge of an insect's wing. Because it looks nearly identical to 'coastal' (relating to the seashore), it is frequently misread or mistyped; the shared Latin root 'costa' explains the resemblance, since the word also gave rise to 'coast' by way of the idea of a rib-like side. Costal is formal and specialist in tone, rarely heard outside clinical, academic, or scientific contexts.
Of or relating to the ribs or the rib cage.
"The X-ray revealed a fracture in one of his costal arches."
Chiefly used in anatomical, medical, and zoological contexts.
(In entomology and zoology) Denoting the anterior or leading edge of a wing or similar structure.
"The costal vein runs along the front edge of the moth's forewing."
A specialized sense within entomology.
One letter separates the sea from your skeleton: 'coastal' belongs to the shoreline, 'costal' to the ribs — both trace back to Latin 'costa', which meant rib before it ever meant coast.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of costal
Costal derives from the Latin noun 'costa', meaning 'rib' or 'side'. It entered English as an anatomical term, likely in the early modern period alongside other Latinate medical vocabulary. The same root produced 'intercostal' (between the ribs) directly, and, through Old French 'coste' meaning 'side or slope', gave rise to the unrelated-in-meaning English words 'coast' and 'accost'.
Related word forms
How costal is actually used
Primarily a technical term used in anatomy, medicine, zoology, and entomology rather than everyday speech. It carries no emotional connotation; register is formal and scientific. In anatomy it most often appears in compound anatomical terms such as costal cartilage, costal margin, and costal pleura.
Easily confused with costal
Coastal means relating to the seashore or coastline, while costal means relating to the ribs.