“Research shows that depth of vocabulary matters to reading comprehension. Children identified as having difficulty in reading comprehension (but who can decode well) do not have the depth of word knowledge that typical readers do. When asked to provide a word definition, they provide fewer attributes. When asked to produce examples of categories (“name as many flowers as you can) they produce fewer. They have a harder time describing the meaning of figurative language, like the expression ‘a pat on the back.’ They are slower and more error-prone in judging if two words are synonyms, although they have no problem making a rhyming judgement.”
Excerpted from: Willingham, Daniel T. The Reading Mind: A Cognitive Approach to Understanding How the Mind Reads. San Francisco: Jossey-Bass, 2017.