Teaching Vocabulary in ESL: A Research-Based Guide for Teachers, With Lesson Ideas

The most effective way to teach vocabulary in ESL is to select words by frequency and need, give students many spaced encounters with each word, make them retrieve words from memory rather than re-read them, and support everything with extensive reading. Presenting a word well matters far less than how often and how actively students meet it afterward.

This guide summarizes the research that matters for classroom practice, then turns it into lesson ideas, a reading plan, a sample week and advice on recommending tools to students.

What vocabulary research tells teachers

1. Frequency decides priority

A small number of words does most of the work in English. The first 2,000 word families cover a large majority of the words in most texts, and Nation (2006) estimated that reading authentic material comfortably takes around 8,000–9,000 families. For teachers, that means two things: make sure students master high-frequency words first, and for academic learners, follow with the Academic Word List (Coxhead, 2000). Rare words that happen to appear in a textbook passage often deserve a quick gloss, not a full lesson.

2. Words need many encounters

One encounter is almost never enough. Studies of learning from reading (Webb, 2007; Waring & Takaki, 2003; Pellicer-Sánchez & Schmitt, 2010) suggest that a word typically needs somewhere around 8–12 or more meetings before it is reliably known, and more for productive use. Waring and Takaki found that many words met only once or twice in a graded reader were forgotten within months. The teaching implication is clear: plan recycling, not just presentation. See how many encounters it takes to learn a word.

3. Retrieval beats review

Roediger and Karpicke (2006) and Karpicke and Roediger (2008) showed that practicing recall produces much better long-term retention than restudying. This is the testing effect. Low-stakes quizzes, recall games and "what was the word for…?" warm-ups are not just assessment; they are the learning itself. More in the testing effect explained.

4. Spacing beats cramming

Distributed practice (Cepeda et al., 2006) produces better retention than massed practice. Revisiting words across lessons and weeks, at expanding intervals, is more effective than intensive work on one day.

5. Input must be comprehensible

Hu and Nation (2000) found that readers needed about 98% known-word coverage to understand fiction without help. At lower coverage, unknown words cannot be inferred from context and reading becomes decoding. This is why graded readers matter for lower levels.

Lesson ideas built on the research

Teach word knowledge in depth, not just meaning

Knowing a word involves more than its definition. Nation (2001) describes word knowledge as including form (spelling, pronunciation, word parts), meaning (including associations) and use (grammar, collocations, register). A student who knows that decision means a choice but writes "do a decision" knows only part of the word. For the most useful words, spend class time on collocations and typical sentence patterns, not only on definitions. For lower-frequency words, recognition may be enough.

Assigning reading that actually builds vocabulary

Most vocabulary growth beyond the first few thousand words comes from reading. The teacher's job is to make sure students read enough, at the right level.

• Match level to coverage. Students should know about 95–98% of words in extensive reading material. A quick check: if a student finds more than two or three unknown words per hundred, the text is too hard for extensive reading. The lexical coverage calculator can help you check a passage.
• Separate extensive and intensive reading. Extensive reading is easy, fast and for pleasure, with few look-ups. Intensive reading is slower, harder and focused on language. Students need both, but most get far too little of the first.
• Give choice. Students read more when they choose topics. A class library of graded readers, or a list of approved websites at the right level, works better than one assigned text.
• Ask for light accountability. A short reading log (title, minutes, three words noticed) keeps reading visible without turning it into homework that kills enjoyment.

A sample week

Recommending tools to students

Most vocabulary learning happens outside class, so teaching students how to learn independently is part of the job. A few principles when recommending tools:

• Match the device. Students who mostly use phones need mobile apps. Students who study and read on a laptop can use browser tools.
• Prefer tools that support retrieval and spacing over tools that only display lists.
• Prefer English-English definitions as level rises. Bilingual dictionaries suit beginners; monolingual learner's dictionaries build deeper understanding at intermediate levels and above.
• Show, do not just tell. Spend ten minutes in class setting a tool up and modeling one session.

For flashcards with full scheduling, Anki and similar apps are strong options, especially if you share a class deck. For learners who read in English online on a laptop, Wordie is one option worth knowing about. It is a Chrome extension: students select a word on any web page to see an English definition, part of speech and synonyms, save it, and from then on it is highlighted whenever it appears on another page, which supports the repeated encounters research recommends. It has a simple recall mode with Forgot / Hard / Easy ratings and a mastery score, and words can be exported to CSV. It needs no account and stores words locally in the browser, which helps in schools with data-protection concerns. There is a free tier (up to 20 saved words) and a low-cost student plan.

Its limits for teachers: there is no class or teacher dashboard, no way to push word lists to students, no mobile app, and no translation into students' first languages. For assigning class word lists and tracking progress, a classroom-oriented flashcard platform is the better choice.

The bottom line

Vocabulary teaching works when it follows a few research-backed principles: teach frequent and needed words first, plan many spaced encounters, make students retrieve rather than re-read, and give them lots of comprehensible reading. Build recycling into every lesson, separate extensive from intensive reading, and spend class time teaching students how to keep learning on their own. For students learning from reading, point them to how to learn vocabulary from reading; for academic classes, the Academic Word List guide.

Sources: Nation, I.S.P. (2001), Learning Vocabulary in Another Language, Cambridge University Press; Nation, I.S.P. (2006), "How large a vocabulary is needed for reading and listening?", Canadian Modern Language Review; Coxhead, A. (2000), "A new academic word list", TESOL Quarterly; Hu, M. & Nation, I.S.P. (2000), Reading in a Foreign Language; Webb, S. (2007), Applied Linguistics; Waring, R. & Takaki, M. (2003), Reading in a Foreign Language; Pellicer-Sánchez, A. & Schmitt, N. (2010), Reading in a Foreign Language; Roediger, H.L. & Karpicke, J.D. (2006), Psychological Science; Karpicke, J.D. & Roediger, H.L. (2008), Science; Cepeda, N.J. et al. (2006), Psychological Bulletin.