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Why can common names such as robin refer to different species in different places?

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A diagram showing the hierarchy of animal classification in taxonomy, with colored boxes arranged from broadest to most specific: domain, kingdom, phylum, class, order, family, genus, and species. — taxonomy Animals and other organisms are classified within a succession of nested groups that ranges from the general to the particular.

Common names like "robin" can refer to different species in different places because they are not standardized and often reflect local naming conventions based on superficial resemblances rather than biological relationships. For example, early colonial settlers in North America named the American robin after the European robin simply because both birds possess an orange or reddish breast, despite belonging to different taxonomic groups.12

Because common names vary across languages, regions, and cultures, they lack the precision required for scientific communication. To resolve this ambiguity, biologists use binomial nomenclature, a standardized system developed by Carolus Linnaeus in the 18th century. This system assigns every species a unique, two-part scientific name—consisting of a genus and a specific epithet—that remains consistent and recognized worldwide, regardless of local common names.23