Crosslinguistic influence (CLI) refers to the different ways in which one language can affect another within an individual speaker. It typically involves two languages that can affect one another in a bilingual speaker. An example of CLI is the influence of Korean on a Korean native speaker who is learning Japanese or French. Less typically, it could also refer to an interaction between different dialects in the mind of a monolingual speaker. CLI can be observed across subsystems of languages including pragmatics, semantics, syntax, morphology, phonology, phonetics, and orthography. Discussed further in this article are particular subcategories of CLI—transfer, attrition, the complementarity principle, and additional theories.