The subject of this research is the dynamic variability in the sphere of personal of the Middle English Period. The object of this research is the personal pronouns of the Middle English (in form of the nominative case) used in the “Canterbury Tales” by Geoffrey Chaucer. Insufficient study of this layer of lexicon necessitates detailed examination of the rich tapestry of variability of pronouns for determination of the area of Medieval language norm that influenced the establishment of modern literary English language, which defines the relevance of this research. The goal consists in description of the dynamic norm of the Middle English. Research methodology consists in systematization, description and classification of language material, extracted through the method of continuous sampling from the first part of the “Knight’s Tale” of the “Canterbury Tales” of Geoffrey Chaucer, and setting quantitative parameters that reveal and confirm linguistic patterns that regularly manifest within the system of personal pronouns of the Middle English. The scientific novelty lies in comprehensive research of variability of personal pronouns and establishment of the dynamic norm and “quasi-norm” of the national literary standard of English language formed in the XIV century. The main conclusion consists in substantiation of the leading role of central dialects in comprising dynamic norm of the Middle English (namely with regards to pronouns), while the forms developed in the north and south should be attributed to quasi-norm.