Size and depth of vocabulary knowledge: what the research shows

Schmitt, Norbert (2014) Size and depth of vocabulary knowledge: what the research shows. Language Learning, 64 (4). pp. 913-951. ISSN 1467-9922

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When discussing vocabulary, a distinction is often made between size of vocabulary (number of known words) and depth of knowledge (how well those words are known). However, the relationship between the two constructs is still unclear. Some scholars argue that there is little real difference between the two, while regression analyses show that depth typically adds unique explanatory power compared to size alone. Ultimately, the relationship between size and depth of vocabulary knowledge depends on how each is conceptualized and measured. In an attempt to provide an empirical basis for exploring the size–depth relationship, this critical synthesis identifies studies that contain measures of both size and depth. Based on a number of different conceptualizations of depth, various patterns emerged. For higher frequency words and for learners with smaller vocabulary sizes, there is often little difference between size and a variety of depth measures. However, for lower frequency words and for larger vocabulary sizes, there is often a gap between size and depth, as depth measures lag behind the measures of size. Furthermore, some types of word knowledge (e.g., derivative knowledge) seem to have generally lower correlations with size than other types.

Item Type: Article
Additional Information: This is the peer reviewed version of the following article: Schmitt, N. (2014), Size and Depth of Vocabulary Knowledge: What the Research Shows. Language Learning, 64: 913–951. doi: 10.1111/lang.12077 which has been published in final form at This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Keywords: Vocabulary Size, Vocabulary Depth, Vocabulary Measurement, Meaning, Formulaic Language, Form-Meaning Link
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Depositing User: Eprints, Support
Date Deposited: 14 Mar 2016 15:35
Last Modified: 13 Oct 2017 03:41

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