For any L2 research project or pedagogical purpose, determining what counts as a single lexical unit is a crucial issue. We would therefore like to thank SSLA for instigating this discussion of the issue, and Stuart Webb for his thoughts on this matter. Although proper perspective must always be maintained, we believe that in thinking about lexical units something of a paradigm shift (Kuhn, 1962) is currently underway in our field: At first, a practice is unquestioned, then conflicting evidence emerges (as has been the case recently on this issue, e.g., McLean, 2018; Stoeckel et al., 2020), alternate approaches become permissible, and eventually a new norm is established. So just what is the emerging norm that appears nascent? Best practice, we would argue, is for researchers and educators to select a lexical unit that is appropriate, considering the evidence, for the learners and use in question. Webb suggests that thus far research has been limited and cautions against the overgeneralization of findings. However, while more evidence is always welcome, it is important to acknowledge that empirical evidence is available. As Brown et al.’s (2020) review found, to date the evidence is that (a) many learners (including those far beyond beginner levels) lack the knowledge necessary to deal with receptive uses of derivational forms of known headwords, and (b) derivational forms

中文翻译：

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词汇单位使用即将发生的范式转变

对于任何 L2 研究项目或教学目的，确定什么是单个词汇单元是一个关键问题。因此，我们要感谢 SSLA 对这个问题的讨论，以及 Stuart Webb 对这个问题的看法。尽管必须始终保持正确的观点，但我们认为，在思考词汇单元时，我们的领域目前正在发生某种范式转变（Kuhn，1962）：首先，一种做法是毫无疑问的，然后出现相互矛盾的证据（正如最近在这个问题上的案例，例如 McLean，2018；Stoeckel 等人，2020），替代方法变得允许，并最终建立了新的规范。那么，刚刚出现的新兴规范是什么？我们认为，最佳实践是让研究人员和教育工作者选择一个合适的词汇单元，考虑到证据，为学习者和有问题的使用。韦伯表示，迄今为止的研究是有限的，并警告不要过度概括研究结果。然而，虽然更多的证据总是受欢迎的，但重要的是要承认经验证据是可用的。正如 Brown 等人 (2020) 的评论所发现的那样，迄今为止的证据是（a）许多学习者（包括那些远远超出初学者水平的学习者）缺乏处理已知词条派生形式的接受性使用所必需的知识，以及（ b) 派生形式