This study aims to describe the general characteristics of language variation and provide concrete examples across diverse communicative contexts. Language variation is a sociolinguistic phenomenon arising from social interaction and varying language functions, divided into categories based on speaker, usage, formality, and communication medium. Speaker-based variation includes idiolect (individual variation), dialect (geographical variation), chronolect (temporal variation), and sociolect (social group variation). Usage-based variation—also known as fungsiolect or register—relates to domains such as academic, journalistic, or legal language. Meanwhile, language formality is classified into five registers: frozen, formal, consultative, casual, and intimate. Finally, variation by medium distinguishes between spoken and written styles, with spoken language being spontaneous and written language more structured. This study employs a descriptive-literature methodology, analyzing key sociolinguistic theories from various sources. The findings indicate that language variation encompasses not only structural aspects (such as phonology, lexicon, morphology, and syntax) but is also significantly influenced by social, geographical, temporal, situational, and modal factors. In conclusion, language variation is a complex phenomenon reflecting the dynamic interplay between linguistic structure and speakers’ social identities, underscoring its importance in studies of social interaction and language education.