1. Sociolinguistics is the study of the effect of social factors on language, including how language varies between social groups based on attributes like ethnicity, education level, and gender.
2. Language usage varies between social classes and regions, which sociolinguistics studies through examining "sociolects".
3. The social aspects of language were first studied in the 1930s but sociolinguistics emerged as a formal field in the 1960s led by linguists like William Labov.