Definition:

SPECIES: The basic unit of classification in biology. Examples are the bald eagle, the white shark, the black widow spider, and the sweetpotato whitefly. The word is both singular (a species) and plural (two species). Species are grouped into a genus (genera, pl.), and genera are grouped into families. The words kind, sort, type, strain, and variety are not part of this classification even though newspaper reporters often use them as if they were.