I analyzed the mental organizations of two sets of fuzzy lexical items by 70 native speakers (NSs) of English and 185 learners of English as a second language (ESL). They provided pair‐wise comparisons of a set of degree adverbs and a set offrequency terms, respectively. I subjected their judgments to unidimensional scaling and circular triad analysis, which indicated that: (a) despite their apparent familiarity with the items, ESL learners' semantic organizations deviated from the NSs' model; (b) the location and extent of semantic mismatch can be identified at different levels of ESL proficiency; (c) consistent approximation to the target model improved as ESL proficiency improves; (d) the structural stability of an individual's private semantic model is not readily generalizable between sets of lexical items or levels of proficiency; and (el consensus among ESL learners improves as proficiency increases. The findings suggest that a discernible approximative pattern exists in the acquisition of ESL semantics, with the differentiation of certain words acquired before the differentiation of others.