Sociolinguistics is the study of how social factors such as ethnicity, gender, age, and socioeconomic class influence language. It examines how language differs between social groups and how these differences can categorize individuals. Sociolinguists study how grammar, vocabulary, and other language aspects vary depending on social context, in contrast to dialectology which focuses on language's effect on society. Key concepts in sociolinguistics include speech communities, prestige varieties, social networks, and differences in language according to class, age, gender, geography, and politeness.