Type-Token Ratio
The type-token ratio (TTR) is the oldest and most widely used measure of lexical diversity: the number of distinct word types in a text divided by the total number of word tokens. A text in which few words repeat yields a TTR near 1, while a text that recycles a small vocabulary yields a TTR near 0. Despite its intuitive appeal and trivial computation, the raw ratio is severely confounded by text length, which has motivated a long line of length-correcting transformations and, ultimately, the more robust indices that have largely superseded it for serious comparison.
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Sources
- Johnson, W. (1944). Studies in language behavior: A program of research. Psychological Monographs, 56(2), 1–15. DOI: 10.1037/h0093508 ↗
- Malvern, D., Richards, B., Chipere, N., & Durán, P. (2004). Lexical Diversity and Language Development: Quantification and Assessment. Palgrave Macmillan. ISBN: 9781403902313
- 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 ↗
How to cite this page
ScholarGate. (2026, June 22). Type-Token Ratio (TTR) for Lexical Diversity. ScholarGate. https://scholargate.app/en/linguistics/type-token-ratio
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
- Measure of Textual Lexical Diversity (MTLD)Linguistics↔ compare
- N-gram AnalysisLinguistics↔ compare
- vocd-D (D Measure)Linguistics↔ compare