Lexical Coverage of TED Talks: Implications for Vocabulary Instruction

Teachers of English are often in search of authentic audio and video materials that promote learners' listening comprehension and vocabulary development. TED Talks, a set of freely available web presentations, could be a useful resource to promote vocabulary instruction. The present replication study examines the lexical coverage of TED Talks by using a corpus comprised of TED Talks presentations. Transcripts of 400 presentations (a total running time of 100 hr and 19 min) were analyzed to determine the vocabulary size necessary to understand 95% and 98% of the words in TED Talks presentations. The findings suggest that 4,000 word families (plus proper nouns and marginal words) provided 95% coverage, and 8,000 word families (plus proper nouns and marginal words) provided 98% of TED Talks presentations. The current study confirms the findings from previous studies that analyzed TED Talks (Coxhead & Walls, 2012) and academic spoken English (Dang & Webb, 2014), suggesting that a wider range of vocabulary (closer to vocabulary coverage for written texts) is necessary to watch and comprehend TED Talks presentations. Based on the findings, the present article provides English language teachers with several learner-friendly suggestions about how TED Talks presentations could be used to expand learners' vocabulary.