Final answer:
Race is a term historically used to categorize people based on physical traits but has been scientifically debunked as a valid biological concept; it's better seen as a social construct, as genetic variation within 'races' often exceeds variation between them.
Step-by-step explanation:
The word that was traditionally used to describe people who are genetically similar but are viewed differently due to phenotypic traits is "race." However, modern science, including biologists, geneticists, and anthropologists, has shown that there is no scientific justification for the concept of race as a biological category. The genetic variation within any given race is often greater than the variation between races, and only a small number of genetic markers are responsible for the physical traits typically used to define race, such as skin color. The term 'race' is thus better understood as a social construct rather than a biological one, and any attempt to classify humanity into distinct racial groups based on genetics is flawed.
Furthermore, the idea that there could be subspecies within humans, equivalent to what is described as "race" in biology, is not supported because humans lack the reproductive isolation seen in speciation. Human biological diversity is real, but it does not align with the racial categories society historically constructed and often emphasizes. It is important to understand the difference between ancestry and race and to focus on ancestry, which is a more accurate reflection of human genetic diversity.