Measure of Textual Lexical Diversity (MTLD)
The Measure of Textual Lexical Diversity (MTLD) is a length-robust index of vocabulary richness introduced by Philip McCarthy in 2005 and validated by McCarthy and Jarvis in 2010. Rather than computing a single ratio over the whole text, MTLD reads the text word by word, tracking a running type-token ratio, and counts how many sequential word runs are needed before the ratio repeatedly falls to a criterion value of 0.720. The mean length of those runs, computed forward and backward and averaged, is the MTLD score — and in validation studies it was the one common index that did not vary systematically with text length.
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Sources
- McCarthy, P. M., & Jarvis, S. (2010). MTLD, vocd-D, and HD-D: A validation study of sophisticated approaches to lexical diversity assessment. Behavior Research Methods, 42(2), 381–392. DOI: 10.3758/BRM.42.2.381 ↗
- McCarthy, P. M. (2005). An assessment of the range and usefulness of lexical diversity measures and the potential of the measure of textual, lexical diversity (MTLD) (Doctoral dissertation). University of Memphis. link ↗
How to cite this page
ScholarGate. (2026, June 22). Measure of Textual Lexical Diversity (MTLD). ScholarGate. https://scholargate.app/en/linguistics/mtld-lexical-diversity
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- Lexical DiversityText mining↔ compare
- N-gram AnalysisLinguistics↔ compare
- Type-Token RatioLinguistics↔ compare
- vocd-D (D Measure)Linguistics↔ compare