This paper examines how the nature of language is represented in science lessons taught through English, and is part of a project investigating the challenges of bilingual education in Hong Kong's junior secondary classes. Educational linguistics, particularly work drawing on systemic functional linguistics, sees language as text and as dialectic. This understanding of language is contrasted with more atheoretical conceptualisations such as language as vocabulary and language as medium. Recordings of the secondary one (Grade 7) science classes, along with interviews with teachers and students and also student questionnaires, were mined for instances where language was foregrounded, for example by explicit reference or by use of L1 Cantonese. These instances were then considered in terms of the conceptualisations of language, and were found to tend towards a language as vocabulary and language as medium orientation. Sample extracts are used to illustrate these points. The disadvantages of these interpretations of the nature of language are discussed, and related to what is currently understood of the role of language in learning science in bilingual settings.