One of the oldest findings in educational research is the strong relationship between vocabulary knowledge and reading comprehension. Word knowledge is crucial to reading comprehension and determines how well students will be able to comprehend the texts they read in middle and high school.

Comprehension is far more than recognizing words and remembering their meanings. However, if a student does not know the meanings of a sufficient proportion of the words in the text, comprehension is impossible. Vocabulary experts agree that adequate reading comprehension depends on a person already knowing between 90 and 95% of the words in a text (Hirsch, 2003). Knowing at least 90% of the words enables the reader to get the main idea from the reading and guess correctly what many of the unfamiliar words mean, which will help them learn new words.

What words should the teacher choose for direct instruction? Teachers should focus on words that are important to the text, useful to know in many situations, and that are uncommon in everyday language but recurrent in books (Juel and Deffes, 2004).

Selecting vocabulary words

Before instruction, preview the text, even when using text that has preselected vocabulary words. Read the passage and identify vocabulary words you think students will find unfamiliar. Ask yourself: 'How difficult is this passage to understand?' Select words that are important to understanding the text. List words you predict will be challenging for your students. You may not be able to teach all of these words. Research supports teaching only a few words before reading. Determine which words are adequately defined in the text. Some may be defined by direct definition and others through context. Expand on these words after reading, rather than directly teaching them before reading.

Identify words students may know based on their prefixes, suffixes and base or root words. If structural elements help students determine words' meanings, don't teach them directly. Consider students' prior knowledge. Words can be discussed as you activate and build prior knowledge. Words can also be extended.

Determine the importance of the word. Ask yourself: "Does the word appear again and again? Is the word important to comprehending the passage? Will knowledge of the word help in other content areas?"

  • Remember, words taught before students read include:
  • Words that will be frequently encountered in other texts and content areas
  • Words that are important to understanding the main ideas
  • Words that are not a part of your student' prior knowledge
  • Words unlikely to be learned independently through the use of context and/or structural analysis.

Adapted from Cooper, J.D. (1997), Literacy: Helping children construct meaning (3rd ed.), Boston: Houghton Mifflin.

Analysing word structure: teaching word parts

When students encounter unknown words they can use knowledge of word parts (root words, suffixes and prefixes) to help determine the meaning. This is especially true when reading content in textbooks because these texts often contain many words that are derived from the same word parts. For example, the Greek root 'bio' (meaning 'life, living organisms') reappears again and again in a typical middle school life science textbook for example, biology, biologist, biosphere, biodegradable, biochemical, biofuel, biohazard). Another example is the prefix 'mono' (meaning 'one, alone, single').

Use of context to determine words meaning

Good readers often use context clues to determine the meanings of unfamiliar words, if they are available in the text. They can locate other words and phrases in a passage that give clues about what an unknown word means. Struggling readers who do not do this should be given direct instruction in how to effectively look for clues or definitions. For example, part of the 'Click and Clunk' strategy (Vaughn et al, 2001) teaches students to follow these steps when they come across a word they do not know (described as a 'clunk').

  1. Reread the sentence with the clunk. Look for key words.
  2. Reread the sentence without the clunk. What word makes sense?
  3. Reread the sentence before and after the clunk. Look for clues.

The clues may be any of the following types of information embedded in the text: definition, restatement, example, comparison or contrast, description, synonym or antonym.

Teach how to effectively use a dictionary

Students need explicit instruction in how to use what they find in a dictionary entry so they are able to transfer that information into something useful. Students may be confused by different meanings for the same word, or the wording in a dictionary entry may be too difficult to read or understand. To choose the right definition, the student must:

  1. use background knowledge about the content in the text
  2. have a sense of the grammatical use in the text
  3. read and understand each definition.

As noted earlier, to remember the meaning of a new word, it is better for students to reword the definition in their own words, to identify synonyms and antonyms for the word, to use the word in their own meaningful sentence, and to recognize that the word may be used differently in other contexts.

For example, indicate the word predatory in the following paragraph:

Call me the youngest dinosaur in the world. Not the kind whose jaws lunge at you out of the phony depths of a 3D movie. The other kind: a dinosaur of outmoded opinion. How outmoded? Let’s just say I consider 3D physically dangerous, economically predatory, artistically self-defeating and imaginatively stunting. That kind of dinosaur.


[pred-uh-tawr-ee, -tohr-ee]


  1. Zoology: preying upon other organisms for food.
  2. of, pertaining to, or characterised by plunder, pillage, robbery, or exploitation: predatory tactics.
  3. engaging in or living by these activities: predatory bands of brigands.
  4. excessive or exploitative in amount or cost, as out of greed or to take advantage of consumers or patrons: predatory pricing.
  5. acting with or possessed by overbearing, rapacious, or selfish motives: He was cornered at the party by a predatory reporter.

Encourage students to insert each definition into the context and to decide if it makes sense. In this case, definition 5 makes most sense in the context.

Ask students to identify other words from this text that they are unfamiliar with and to find out what they mean. These words may include: outmoded, artistically self-defeating, imaginatively stunting.


Australian curriculum  – ACELY1733: Interpreting, analysing, evaluating: Apply increasing knowledge of vocabulary, text structures and language features to understand the content of texts.

NSW syllabus  – EN4-1A: Apply increasing knowledge of vocabulary, text structures and language features to understand the content of texts

NSW literacy continuum  – Vocabulary knowledge, Cluster 13, Marker 1: Applies knowledge of root words and word origins to understand the meaning of new subject specific words. Vocabulary knowledge, Cluster 13, Marker 4: Uses a combination of effective strategies to work out the meaning of unknown words.

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