A species is one particular kind of living thing — lions are one, tigers another. An endangered species, a new species, the human species.
The usual test is whether two populations breed and produce fertile young, and it fails often enough — ring species, hybrids, everything asexual — that biologists keep several definitions and pick by the job. The word is the same in singular and plural. Note that the Latin means appearance, and spice is the same word.
1nounspeciesOne particular kind of living thing.
“The tiger is an endangered species, and very few are left in the wild.”
species is a category of living things.
Latin species means appearance or kind, from specere, to look. Spice, special and spectacle come from the same looking.
Proto-Indo-European
*speḱ-
Latin
speciēs — appearance; quality
English, today
species
Built from
From Latin speciēs (“appearance; quality”), from speciō (“see”) + -iēs suffix signifying abstract noun. a doublet of spice.
Etymology from Wiktionary, CC BY-SA