Scientific names of plants have two words, the genus name and the species name, often called the specific epithet. Determination of the scientific name, also called the binomial, of a plant specimen is the goal of plant identification. For example, Serenoa repens is the scientific name of what is commonly called saw palmetto. Serenoa is the genus name and repens is the specific epithet. Both words are Latinized.
Before modern botany, when humans lived in isolated tribes, we informed each other where there were good plants in our local region that we could safely eat or harvest for medicine or clothing. Plant identification skills including naming plant species were based on comparison with related or similar species according to their morphological shape or size or color. Not surprisingly the “kind” of plant recognized traditionally as a “common name” is often the same as the species in the modern taxonomic concept of a species identified by a scientific name. So the concept of a species is the same, just under a different name.
Common names
Common names in local dialects have helped for millennia in communication but are not a framework for international systematic taxonomy. There are many practical advantages of an organized system that is aloof from daily local communications in the marketplace, and that is not tied to regional dialects, and that can be used across tribes and boundaries.
Problems with common names are that they are sometimes applied to more than one species, and one species can have multiple common names. Scientific names provide that each scientific name applies to only one species, and each species has only one accepted binomial or scientific name. When there are discrepancies or conflicts, international rules of nomenclature resolve such conflicts by going back to the earliest published use (“priority”) of a species name. And rules of nomenclature flexible to make orderly changes. When there are changes in concept of species, the species can be formally transferred to another genus, preserving the original concept while recognizing a change in relationship.
“Specific epithet”
It can be confusing that the “species” is the entity being identified and named, and the second word in the binomial is called the “species name” or the “specific epithet.” Without a genus name, the second word, the “specific epithet,” does not refer to any one thing.
The specific epithet “repens” in the binomial “Paspalum repens” is repeated in other binomials such as Serenoa repens. and is not used by itself. Therefore, to be clear, a binomial or scientific name is not a genus and a species but is a genus name and species name or specific epithet.
Plant genus names are not recycled. There is only one Paspalum and one Serenoa. So it is okay to use a plant genus name by itself as representing all the species within that genus, such as Paspalum notatum, Paspalum repens, and Paspalum vaginatum. For shorthand, after first mention, the genus name can be abbreviated, e.g., Paspalum notatum, P. repens, and P. vaginatum.
Scientific names are commonly written as italic letters or sometimes they are underlined. This is a typographical style for readers and is never required.