The apparent-time hypothesis is a methodological construct in sociolinguistics whereby language change is studied by comparing the speech of individuals of different ages. If language change is taking place, the apparent-time hypothesis assumes that older generations will represent an earlier form of the language and that younger generations will represent a later form. Thus, by comparing younger and older speakers, the direction of language change can be detected.

The apparent-time method allows change to be studied by synchronic analysis, which examines the state of the language at a particular point in time. That contrasts with real-time sociolinguistics, which compares data from two points in time to observe change directly.

Apparent-time analysis assumes that most features of language are acquired during childhood and remain relatively unchanged throughout an individual's lifetime once that individual is past a certain age. Therefore, a speaker's speech is a reflection of speech patterns acquired during language learning as a child.

The apparent-time hypothesis depends on several assumptions: a significantly broad sample is taken to be representative of the population, and vernacular speech is relatively stable in a given individual after adolescence. Apparent-time studies are examples of cross-sectional studies in which a population group is examined at a certain point in time.

Within the population, age-stratified variation is assumed to reflect the ages at which members of the population learned language. It is often contrasted with real-time studies, which are examples of longitudinal studies.

The most direct way of investigating a population's usage of linguistic variants is through surveys and interviews. In the case of apparent-time studies, surveys are conducted in a population across a broad age range to investigate the linguistic variants across a broad age spectrum. Theoretically, patterns of use should differ between different age groups.

Data gathered from real-time sociolinguistics studies can also be used for apparent-time sociolinguistics. However, apparent-time data are only a surrogate for real-time evidence and care must be made before they are considered to represent diachronic linguistic developments.

The apparent-time hypothesis allows sociolinguists the convenience of gathering data at one point in time or analyzing past data from historical linguistic studies that cannot be replicated. For real-time sociolinguistics, the same participants of the study must be recruited and tested at later times to validate the data, which is a method that is difficult to implement. However, real-time corpora can also be used for apparent-time analyses.