Citron
There are also a number of citron hybrids; for example, ponderosa lemon, the lumia and rhobs el Arsa are known citron hybrids, some are claiming that even the Florentine citron is not pure citron, but a citron hybrid.
Citrus
The generic name originated from Latin, where it referred to either the plant now known as citron ("C. medica") or a conifer tree ("Thuja"). It is somehow related to the ancient Greek word for cedar, κέδρος ("kédros"). This may be due to perceived similarities in the smell of citrus leaves and fruit with that of cedar. Collectively, "Citrus" fruits and plants are also known by the Romance loanword "agrumes" (literally "sour fruits").