In general terms, sociolinguistic theory examines all of the ways in which society, by its organization, norms and institutions, exerts power over language and its use. Sociolinguistic theory should thus be differentiated from the sociology of language, which examines the opposite train of influence, that of language over society.
One common characteristic of sociolinguistic theory is that it tends to examine the effects of society on language through what American linguist William Labov has called "secular linguistics." By this, Labov indicates a theory of language departing from Noam Chomsky's often cited presumption that language and its use can be wholly dissociated from social context. In other words, Chomsky's framework suggests that language exists and can be examined outside its social use, a position many sociolinguistic theorists deny.
Sociolinguistic theory is often applied through a specific methodology. Usually, linguistic variables are selected by researchers. Then, these researchers randomly choose individuals from certain sections of the population, subjects called "informants." The researchers subsequently examine the frequency with which the pre-selected linguistic variants are used, after which they examine those results in light of various social indices, such as class, income level, education, gender, age and ethnicity from which the informants were derived. In this way, sociolinguists claim to be able to chart the innovations in accent and dialect regionally and over time as they pertain to social phenomena, according to Richard Nordquist at About.com.