The paper focuses on the semantic derivation models of irrational vocabulary -- a semantic class of words that denote the situation of experience that is not based on logical reasoning or clear thinking. The study shows the characteristics of the development of an irrational vocabulary semantic paradigm and reveals semantic derivation models of irrational verbs and adjectives in the English language. It is posited that semantic derivation strategies are realised simultaneously with the changes of the situation and actants profiles. The change of a situation profile suggests the shift in the experiencer's vantage point, i.e. gnoseological (either perceptual or evaluative) position from which a situation is considered. The change of an actant profile provides for the shifts at the level of participants and their characteristics. The changes are thought to determine the types (models) of semantic shift strategies that underlie the development of the irrational words' semantic paradigms. The analysis of the semantic shift strategies of irrational verbs and adjectives in English shows that the concept of irrationality may extend to the boundaries of the internal (occurring within the hierarchy of the person's inner systems) and external (occurring within the hierarchy of the person's values) conceptual domains. The study concludes that irrational verbs and adjectives in English may apply to the following semantic shift strategies: role (reduced to the changes of the participant's type or structure), pragmatic (reduced to the changes of the participant's communicative rank), deictic (reduced to the changes of the participant's positional characteristics) and taxonomic (reduced to the changes of the participant's categorical class).