Are English medium science teachers effective teachers of English vocabulary?

This paper describes how English medium teachers of science construct the meaning of important new subject-specific vocabulary with students. The strategies used by some teachers include both explicit and implicit vocabulary teaching techniques including the use of definitions and paraphrases, grammatical functions, and repetition, especially with an ever-widening range of associations. Students’ understanding of word (and science) meaning is, thereby, enriched and expanded. Other teachers do very little to help their students learn the meanings of new words. Among most teachers, however, some aspects of word meaning and use are neglected and some important and useful English vocabulary is ignored. The paper considers how the vocabulary teaching techniques which these teachers find valuable match those endorsed by the literature and supported by research on second language vocabulary teaching and learning. It concludes that some of the teachers of science are highly effective teachers of English as a second language within the confines of their subject but that the full benefit of using of English as a medium of instruction is lost because the teachers view their role too narrowly. Others would benefit greatly from the use of second language vocabulary teaching techniques but these are only likely to be adopted if they can be seen to contribute to subject teaching and learning.