A species is commonly defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically through sexual reproduction. This biological species concept emphasizes reproductive isolation as a key factor distinguishing one species from another

. However, defining a species is complex and there are many concepts used by scientists. Besides reproductive capability, species can also be distinguished by characteristics such as morphology (form and structure), genetics (DNA sequences and gene pools), behavior, ecological niche, and evolutionary lineage

. For example, some species concepts focus on ecological roles or genetic similarity rather than just interbreeding ability. Challenges to the species concept arise with organisms that reproduce asexually, hybridize, or form species complexes where boundaries are unclear. In such cases, the traditional biological species concept does not always apply, and alternative definitions or integrative approaches combining multiple data types are used

. In taxonomy, a species is the fundamental unit of classification and is given a two-part Latin name (binomial nomenclature), consisting of the genus name followed by the specific epithet (e.g., Homo sapiens)

. In summary, a species is generally understood as a group of organisms capable of interbreeding and producing fertile offspring, but the full definition varies depending on the context and organism group, reflecting the complexity of life and evolution