The Middle English creole hypothesis is the concept that the English language is a creole, i.e. a language that developed from a pidgin. The vast differences between Old and Middle English have led some historical linguists to claim that the language underwent creolisation at around the time of the Norman Conquest. The theory was first proposed in 1977 by C. Bailey and K. Maroldt and has since found both supporters and detractors in the academic world. Different versions of the hypothesis refer to creolisation through contact between Old English and Norman French, between Old English and Old Norse, or caused by large numbers of people switching from speaking British Celtic languages to speaking English. Some versions of the hypothesis actually propose multiple creolization events, with later ones reinforcing and broadening simplifications introduced by earlier ones.
The argument in favour of calling Middle English a creole comes from the extreme reduction in inflected forms from Old English to Middle English. The system of declension of nouns was radically simplified and analogized. The verb system also lost many old patterns of conjugation. Many strong verbs were reanalysed as weak verbs. The subjunctive mood became much less distinct. Syntax was also simplified somewhat, with word order patterns becoming more rigid. These grammatical simplifications resemble those observed in pidgins, creoles and other contact languages, which arise when speakers of different languages need to communicate. Such contact languages usually lack the inflections of either parent language, or drastically simplify them. However, many say that English is probably not a creole because it retains a high number (283) of irregular verbs, just like other Germanic languages, a linguistic trait that is usually first to disappear among creoles and pidgins.
It is certain that Old English underwent grammatical changes, e.g. the collapse of all cases into genitive and common. However, the reduction of unstressed vowels to schwa, due to a fixed stress location, contributed to this process, a pattern that is common to many Germanic languages. The process of case collapse was also already under way in Old English, e.g. in strong masculine nouns, where the nominative and accusative cases had become identical. Thus the simplification of noun declension from Old English to Middle English may have had causes unrelated to creolization, although creolization may have caused the grammatical changes to occur more rapidly.
English has numerous French and Norman loanwords, borrowed mostly during the 14th century. English began to replace French as England's official national language by 1362 when, under Edward III, Parliament was addressed in English for the first time since the Norman Conquest of 1066.
Nevertheless, the Norman invasion had still resulted in the loss of many native Anglo-Saxon words. In fact, by the end of the period in which Middle English was spoken, as much as eighty percent of Old English vocabulary was no longer in use. However, the most striking Norse borrowing (their pronouns) cannot be attributed to creolisation. It was more likely a result of ambiguity between hiem and him etc.
The most common plural form in English is descended from the masculine nominative-accusative plural (Old English -as) and is also cognate with the Old Saxon plural -os and the Old Norse plural -ar. However, the widespread use of the -s plural may suggest French influence. No other Germanic language has just one pattern of regular plural formation: Dutch and Afrikaans have two, whereas German and Swedish have at least five (or more, depending on definition).
French influence has affected English pronunciation as well. Whereas Old English had the unvoiced fricative sounds [f], [s], [?] (as in thin), and [?] (shin), French influence helped to distinguish their voiced counterparts [v], [z], [ð] (the), and [?] (mirage), and also contributed the diphthong [?j] (boy). The combination of a largely French-speaking aristocracy and a largely English-speaking peasantry gave rise to many pairs of words with a Latinate word in the higher register and a Germanic word in the lower register (e.g., French poultry vs Germanic chicken).