Nineteenth-century concepts of race were closely tied to the terminology used by scientists and others to delineate human differences. The definition of a scientific concept constrains not only its meanings but also its potential relationships to other concepts. Ethnologist James Cowles Prichard redefined the taxonomical terms species, variety, and permanent variety in order to change the scientific and social meanings of racial difference. In doing so he laid claim to the "problem of race" on behalf of the young science of ethnology.