The thesis investigates phraseological transformation, contamination and occasional paradigm expansion as sources of semantic ambivalence. The analysis is based on English, Russian and Uzbek examples in which a stable expression is reinterpreted through context. The study shows that phraseological ambivalence appears when an idiom is understood both as a fixed expression and as a free combination of words. Contamination creates a hybrid form in which two phraseological prototypes are simultaneously recognizable. Occasional paradigm expansion occurs when a text temporarily includes a foreign unit into an existing semantic series on the basis of phonetic, graphic or morphological similarity. These mechanisms reveal the semantic productivity of the tension between linguistic norm and contextual innovation.