The multidimensional conceptualization of vocabulary knowledge has been extraordinarily influential in lexical research. Yet, the few studies that have empirically explored the structure of word knowledge conflict regarding its multidimensionality. The present study examines the nature of L2 vocabulary knowledge by exploring how the hypothesized word-knowledge dimensions fit together across different L2 learner groups. A total of 314 EFL learners from two dissimilar L1 backgrounds (Chinese n = 170; Spanish n = 144) were assessed using eight vocabulary measures testing recognition and recall knowledge of form-meaning, collocations, multiple meanings, and derivatives. Confirmatory factor analysis (CFA) revealed that vocabulary knowledge behaves as a unidimensional construct for each learner group individually. Simultaneous multigroup CFA confirmed that this unidimensional model holds invariant across the two groups regardless of their distinct L1s. These findings provide empirical evidence for the unidimensionality of vocabulary knowledge in a second language, indicating the need to refine the conceptualization of the construct.

词汇知识的多维概念化在词汇研究中具有非凡的影响力。然而，少数实证探索词汇知识结构的研究在其多维性方面存在冲突。本研究通过探索假设的单词知识维度如何在不同的二语学习者群体中组合在一起，来检验二语词汇知识的性质。共有 314 名来自两种不同 L1 背景的 EFL 学习者（中文n = 170；西班牙语n= 144) 使用八项词汇量度进行评估，测试识别和回忆形式意义、搭配、多重意义和派生词的知识。验证性因素分析 (CFA) 表明，词汇知识表现为每个学习者群体单独的一维结构。同时进行的多组 CFA 证实，该一维模型在两组之间保持不变，无论其 L1 是否不同。这些发现为第二语言中词汇知识的单维性提供了经验证据，表明需要改进结构的概念化。