Non-Linear Relationship Between Word Frequency and Second Language Vocabulary Acquisition

Word frequency has long been recognized as a key factor in second language vocabulary acquisition (SLVA), yet its role across different lexical categories warrants further investigation. This study aims to examine the mechanisms by which word frequency shapes SLVA. A total of 100 third-year female undergraduates from a foreign language university, equally divided between English majors and non-English majors, participated in the study. Focusing on prepositions, polysemous words, and homophones, the research combined questionnaire data with quantitative analyses to assess the frequency–acquisition relationship. The results show that the frequencies of polysemous words and homophones are positively associated with acquisition outcomes, whereas the frequency of prepositions displays a negative effect. Cross-lexical analyses and computer-generated curves further reveal a significant nonlinear relationship between word frequency and SLVA. Chi-square tests confirm that the frequency effect is consistent across both English majors and non-English majors. These findings contribute to a more nuanced understanding of frequency effects in SLVA and provide pedagogical implications for vocabulary instruction.