Which definition accurately describes an endangered species?

The correct definition of an endangered species is that it refers to a species at risk of extinction. This classification reflects the significant decline in population or habitat loss that threatens the survival of the species. Endangered species are often vulnerable due to various factors, including environmental changes, loss of habitat, overexploitation, and competition with invasive species.

In contrast, a species that is expanding its habitat does not fit the criteria for being endangered; rather, it suggests a species that is thriving or adapting successfully to new environments. Similarly, a species that is increasing in population indicates that it is not at immediate risk of extinction, and thus would not be categorized as endangered. Lastly, a species commonly found in urban areas does not necessarily imply any risk to survival; urban adaptability can vary greatly among species and does not inherently relate to their conservation status. Overall, the essence of an endangered species revolves around the immediacy of the threat to its existence, making the definition of being at risk of extinction the most accurate.