There isn't a single, universally accepted definition of a species in biology, as the concept is complex and can vary depending on the specific organism and context. However, the most widely accepted definition is the Biological Species Concept (BSC), which states:

"A species is a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups."

Here's what this means:

* Interbreeding: Members of the same species can reproduce with each other and produce fertile offspring.

* Natural Populations: These populations occur naturally in the wild, not just in captivity.

* Reproductive Isolation: Members of different species cannot interbreed or produce fertile offspring.

Limitations of the BSC:

The BSC has limitations, especially when applied to:

* Asexual organisms: These organisms don't reproduce sexually, so the concept of interbreeding doesn't apply.

* Extinct species: Determining interbreeding potential is impossible for species that no longer exist.

* Hybrids: Some species can produce fertile offspring even though they are considered distinct.

Other Species Concepts:

Other species concepts exist, such as the:

* Morphological Species Concept: Species are defined based on physical characteristics.

* Phylogenetic Species Concept: Species are defined as the smallest group of organisms sharing a common ancestor.

* Ecological Species Concept: Species are defined by their ecological niche.

While the BSC is the most widely accepted, the most appropriate species concept can vary depending on the research question and the specific organism being studied.