Lexical threshold revisited: Lexical text coverage, learners’ vocabulary size and reading comprehension

We explore the relationship between second language (L2) learners’ vocabulary size, lexical text coverage that their vocabulary provides and their reading comprehension. We also conceptualize “adequate reading comprehension” and look for the lexical threshold for such reading in terms of coverage and vocabulary size. Vocabulary size was measured by the Levels Test, lexical coverage by the newest version of Vocabulary Profile and reading comprehension by a standardized national test. Results show that small increments of vocabulary knowledge contribute to reading comprehension even though they hardly improve text coverage. We suggest two thresholds: an optimal one, which is the knowledge of 8,000 word families yielding the coverage of 98% (including proper nouns) and a minimal one, which is 4,000–5,000 word families resulting in the coverage of 95% (including proper nouns).