"Language develops over time and sociocultural change is reflected in changes in vocabulary" That is true and inevitable in a language that is alive . When languages are in contact , they , undoubtedly, influence one another. In such cases, languages phenomena like borrowings or loan words and calques (semantic or syntactic calques) appear. The only languages that do not evolve are dead languages . Some language purits call it " contamination " when, in fact , that should be called language development.
Other linguistic variations are those related to time (historical variations) and geography. Thanks for another first-class post.