Beyond the first several thousand most commonly used words in a language, direct vocabulary instruction is not efficient. Use of inferential skills then becomes the most effective way of learning new vocabulary; it is the way native speakers build their 60,000 word vocabularies. Because the skill is not automatically transferable, it must be systematically taught to students of foreign languages. This task is best accomplished with a good classification scheme for context clues. An improved classification system that uses grammatical as well as semantic clues and that stresses both structural and semantic dimensions has been developed. It consists of four overall categories: direct-explanation, overall-context, trans-sentence, and intra-sentence clues. For each of the last two categories there are two dimensions, structural and semantic. The scheme can be useful for native English speakers, learners of English, and learners of other foreign languages. Five tables display each category, including definitions, examples, and illustrative sentences. (MSE)