costa
n. countable C2 Proficiency US //ˈkɔstɑ// UK //kˈɒstɐ// cos·ta
n. the edge of a leaf or a bird's wing. In plants, it is the main vein that runs along the side of a leaf.
n. the leading edge of an insect's wing or the primary longitudinal vein of a leaf. In botanical contexts, it refers specifically to the rib or midvein that provides structural support.
The scientist examined the costa of the leaf under a microscope.
The primary costa of the specimen was unusually thick, suggesting the plant had adapted to high winds.
In many species of ferns, the arrangement of the sori along the costa serves as a primary diagnostic feature for field identification.
Usage
The plural form is 'costae'.