In sociolinguistics, a sociolect is a form of language (non-standard dialect, restricted register) or a set of lexical items used by a socioeconomic class, profession, age group, or other social group.

Sociolects involve both passive acquisition of particular communicative practices through association with a local community, as well as active learning and choice among speech or writing forms to demonstrate identification with particular groups. The term sociolect might refer to socially restricted dialects, but it is sometimes also treated as equivalent with the concept of register, or used as a synonym for jargon and slang.

Sociolinguists—people who study sociolects and language variation—define a sociolect by examining the social distribution of specific linguistic terms. For example, a sociolinguist would examine the use of the second person pronoun you within a given population. If one distinct social group used yous as the plural form of the pronoun, then this could indicate the existence of a sociolect. A sociolect is distinct from a regional dialect (regiolect) because social class, rather than geographical subdivision, substantiates the unique linguistic features.

A sociolect, defined by leading sociolinguist and philosopher Peter Trudgill, is "a variety or lect which is thought of as being related to its speakers' social background rather than geographical background." This idea of a sociolect began with the commencement of dialectology, the study of different dialects in relation to society, which has been established in countries such as England for many years, but only recently has the field garnered more attention. However, as opposed to a dialect, the basic concept of a sociolect is that a person speaks in accordance with their social group whether it is with regard to one's ethnicity, age, gender, etc. As William Labov once said, "the sociolinguistic view ... is that we are programmed to learn to speak in ways that fit the general pattern of our communities." Therefore, what we are surrounded with in our environment determines how we speak; hence, our actions and associations.

The main distinction between sociolects (social dialects) and dialects proper (geographical dialects), which are often confused, is the settings in which they are created. A dialect's main identifier is geography: a certain region uses specific phonological, morphosyntactic or lexical rules. Asif Agha expands the concept by stating that "the case where the demographic dimension marked by speech are matters of geographic provenance alone, such as speaker's birth locale, extended residence and the like". However, a sociolect's main identifier is a socioeconomic class, age, gender, and/or ethnicity in a certain speech community.

An example of a dialectal difference, based on region, is the use of the words soda or pop and coke in different parts of the United States. As Thomas E. Murray states, "coke is used generically by thousands of people, especially in the southern half of the country." On the other hand, pop is known to be a term that is used by many citizens in the northern half of the country.

An example of a sociolect difference, based on social grouping, is the zero copula in African American Vernacular English. It occurs in a specific ethnic group but in all areas of the United States. William Labov gives an example: "he here" instead of "he's here."

Code switching is "the process whereby bilingual or bidialectal speakers switch back and forth between one language or dialect and another within the same conversation".