In one sense of ‘a language’, X is said to be a language if it is distinct to some specified degree from all other languages, i.e., X and Y are two languages if they differ beyond a certain criterion (e.g., of structural similarity, shared historical change, mutual intelligibility, or speaker’s attitudes); otherwise they are varieties of one language. In another sense of ‘a language’, X is said to be a language if it has some minimal degree of stability. Although all languages in active use are in a state of flux, when the flux apparent in a given set of data X is greater than a certain degree, then X is regarded as transient, incipient, or approximative to a language, rather than being itself a language. In the third sense, X is said to be a language if it is a code with several levels of structure corresponding to phonological, morphosyntactic, lexical, and discourse regularities shared by a community of speakers, and if it is used in a wide range of communicative functions. In this sense a variety without such levels and uses may be called a special language, restricted language, or register, and may be regarded as part of, supplementary to, or parasitic on a full language.
- Ferguson-DeBose (1977), a pag.111-112

To be recognized as a language a pidginized variety must be sufficiently different from the source languages to be mutually unintelligible without special exposure and acquisition, and it must be felt by its users to be a separate entity. It must also be sufficiently homogeneous and stable to be described by a single grammar with variation rather than combination of grammars. And, perhaps most critical, it must be sufficiently elaborated (“depidginized”).
- Ferguson-DeBose (1977), a pag.112