Every reader possesses five distinct vocabularies--listening, speaking, reading, writing, and potential--which grow at different rates, depend on the background and motivation of a particular reader, and are positively related to overall intelligence and reading comprehension. If students are to gain complete understanding of reading material in content areas, they must be exposed to a well-developed program of vocabulary enlargement in every subject area. Content area teachers must develop a careful program for building these skills based on at least eight important principles, including introducing the words chosen for study as part of a sentence and never in isolation, providing meaningful exercises and lessons for practice with newly learned words, and informing students that a single word may represent many different parts of speech and have different meanings depending on sentence structure. Activities based on these principles include having students underline words in a text passage, write the definition they think is appropriate, and match definitions with respective words. Finally, evaluating students' vocabulary skill development can be done with commercial reading tests or a cloze procedure test. (HTH)