We use nicknames, Meg, Margie, Maggie, Peggy. These are like names of plant varieties. The variety is a subgroup name in which the plant differs only slightly from the species. This further delineates a specific plant. It is shown in Latin notation following the genus and species and the abbreviation var.
Hybrid plants are cultivars.
The cultivar name is set off in one of three ways - by putting the abbreviation cv. By the way, the italics are used only because it is proper, in writing, to italicize words that are in any language other than English. Each Latin botanical name is actually a fascinating puzzle that can tell you a great deal about the plant and how it is identified. So Mentha piperata is peppery mint. Sometimes we can recognize only part of the plant name, but it may be possible to guess the rest, since many English words are derived from Latin.