Lexical bundles perform discourse functions and present differing levels of variability, with some slots replaceable by optional words. Incorporating both function and formulaicity perspectives is a promising approach to uncover certain features of these recurrent language patterns. Based on the variability measurement and functional taxonomy proposed by Biber (2009) and Biber et al. (2004), this study compared the extent to which the lexical bundles from research articles of applied linguistics and pharmaceutical sciences are fixed. Thereafter, the lexical bundles were examined across the discourse functions to explore the possible interaction between function and variability. The results indicate that variability shows disciplinary variation, with bundles from applied linguistics articles as a whole being relatively less fixed. In addition, discourse functions are found to be closely associated with variability. These findings shed light on the question of whether lexical bundles are prefabricated patterns and may facilitate the teaching of academic writing at the graduate level.

词汇束执行话语功能并表现出不同程度的可变性，其中一些插槽可以用可选单词替换。结合功能和公式性观点是揭示这些递归语言模式某些特征的有前途的方法。基于Biber（2009）和Biber等人提出的变异性度量和功能分类法。（2004年），该研究比较了应用语言学和药学领域的研究文章中的词汇束被固定的程度。此后，检查了语篇功能中的词汇束，以探索功能和可变性之间可能的相互作用。结果表明，变异性表现出学科差异，从整体上来说，来自应用语言学文章的丛集是相对固定的。此外，话语功能被发现与变异性密切相关。这些发现揭示了词汇束是否为预制形式的问题，并可能有助于研究生阶段的学术写作教学。