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Vocabulary Breadth and How to Develop It

Updated: May 7

At the TESOL 2024 Convention in Tampa Florida, March 2024, I had the pleasure of presenting on a panel on vocabulary selection for ESL materials development organized by Larry Zwier from the Reading and Vocabulary Interest Section and Taylor Sapp from Materials Writers Interest Section of TESOL International Association. My co-presenters are esteemed colleagues, Charlene Polio from Michigan State University, Scott Roy Douglas from University of British Columbia, and Clare Hambly from Oxford University Press. Each shared valuable information and resources for selecting and teaching vocabulary essential for students to use English effectively for academic studies and professional purposes.

Inspired by Scott Roy Douglas' presentation about vocabulary thresholds and coverage and his idea of blanking out words that students may not know when they read, I created four graphics to illustrate how much English learners can understand a piece of academic writing, if they know around 76%, 86%, 95%, and 98% of the words in the text (see Douglas (2014) for more information). The percentage of known words in a text is also known as vocabulary coverage of lexical coverage.

Past research suggests that if a learner knows 2,000 word families, they will have coverage of 76% of the words in an English text, which means they encounter an unfamiliar word one in four times. If they know 2,570 word families, this coverage is 86%. If they know 4,000-5,000 word families, the coverage is 95% while 8,000-9,000 word families will get them 98% coverage, which allows them to read independently with adequate comprehension (e.g. Coxhead, 2000; Laufer & Ravenhorst-Kalovski, 2010; Nation, 2006, Schmitt, Jiang, & Grabe, 2011). Sanchez (2022) also revisits this concept in her research in this presentation.

To have a sense of your comprehension level when reading a text with 76% vocabulary coverage, you may try reading this passage that I wrote a while ago with 25% of the words blanked out.

The images below show different levels of coverage. Overall, it has been concluded that learners need about 8,000 to 9,000 word families in order to read a variety of texts independently with adequate comprehension in English.

This illustrates the importance of vocabulary in reading and listening comprehension in particular and the concept of "proficiency" in general.

However, no matter how important vocabulary is, we wouldn't want to teach vocabulary in isolation through word lists and memorization alone. In our panel on vocabulary selection for materials development, we shared the following ideas.

1. Word lists can be helpful in developing materials so that learners' vocabulary can be expanded for increased coverage. Some popular word lists include the General Service List (GSL), Academic Word List (AWL), Academic Spoken Word List (ASWL), Academic Vocabulary List (AVL), and Oxford Word Lists for English learners.

2. The starting point of teaching vocabulary is still texts and tasks and especially authentic texts because only through extensive exposure to texts do learners acquire the kind of vocabulary that is actually used in different genres and situations. In addition, Charlene Polio highlights the importance of teaching multiword units such as idioms for academic. See Miller's (2020) article The bottom line: Are idioms used in English academic speech and writing?

3. Scott R. Douglas shared a method that I was very intrigued by called "spiked proficiency" in the context of academic English language instruction at a university in Canada. Instruction is organized around themes/contents that mirror what they may encounter in undergraduate and graduate studies at university. They will develop more vocabulary (or a spike) in that particular theme or content area. Then they move on to other areas for more "spikes" and expansion of vocabulary coverage.

Some articles and resources shared by the panel:

Here are our TESOL selfies and picture at the panel presentation.

There you have it! If you share the graphics, please give me and Scott credit.

About the author: Dr. Linh Phung is a dedicated international educator, innovator, and leader with a proven track record of directing successful educational programs, fostering academic excellence, and driving innovation in language learning. With Eduling, she leads a cross-functional team of IT developers, content developers, and designers in the development of Eduling Speak, an app that connects learners to talk in pairs based on 1200+ communicative tasks and games. She's also a published author and expert in language education with publications in high impact journals, experienced in leadership roles, and committed to enhancing educational experiences and outcomes. She currently serves as an English Language Specialist with the U.S. Department of State.

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