“Looking words up in a dictionary will be of limited use—not useless, but, but we must acknowledge that it will be just one context in which to understand the word’s meaning, and it’s possible that the student will misunderstand the definition. Explicit instruction of new words is more likely to be successful the way teachers usually implement it, with multiple examples and with the requirement that students use each word in different contexts. There is a good evidence that students do learn vocabulary this way.
In addition to consistent vocabulary instruction, teachers can make it more likely that students will learn words they encounter in context. They can give students pointers that will help them use context for figure out an unfamiliar word. For example, students can learn to use the clues in the sentence about the unknown word’s part of speech, to use the setting described in the text to constrain the word’s meaning, and to use the tone of the text to help constrain meaning.”
Excerpted from: Willingham, Daniel T. The Reading Mind: A Cognitive Approach to Understanding How the Mind Reads. San Francisco: Jossey-Bass, 2017.