<P> The geographic range over which a particular common name is used varies; some common names have a very local application, while others are virtually universal within a particular language . Some such names even apply across ranges of languages; the word for cat, for instance, is easily recognizable in most Germanic and many Romance languages . Many vernacular names however, are restricted to a single country, and colloquial names to local districts . </P> <P> Common names are used in the writings of both professionals and laymen . Lay people sometimes object to the use of scientific names over common names, but the use of scientific names can be defended, as it is in these remarks from a book on marine fish: </P> <Ul> <Li> Because common names often have a very local distribution, we find that the same fish in a single area may have several common names . </Li> <Li> Because of ignorance of relevant biological facts among the lay public, a single species of fish may be called by several common names, because individuals in the species differ in appearance depending on their maturity, gender, or can vary in appearance as a morphological response to their natural surroundings, i.e. ecophenotypic variation . </Li> <Li> In contrast to common names, formal taxonomic names imply biological relationships between similarly named creatures . </Li> <Li> Because of incidental events, contact with other languages, or simple confusion, common names in a given region will sometimes change with time . </Li> <Li> In a book that lists over 1200 species of fishes more than half have no widely recognised common name; they either are too nondescript or too rarely seen to have earned any widely accepted common name . </Li> <Li> Conversely, a single common name often applies to multiple species of fishes . The lay public might simply not recognise or care about subtle differences in appearance between only very distantly related species . </Li> <Li> Many species that are rare, or lack economic importance, do not have a common name . </Li> </Ul> <Li> Because common names often have a very local distribution, we find that the same fish in a single area may have several common names . </Li>

What is the purpose of giving organisms a scientific name instead of simply using common names
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