Definitions in Science Lectures JOHN FLOWERDEW City Polytechnic of Hong Kong This paper is an empirical study of the speech act of definition in science lectures. Definitions occurring in sixteen lectures by native speaker biology and chemistry lecturers to non-native speaker students were transcribed and coded onto a computer data base, according to twenty-eight linguistic and para- linguistic features. Data were obtained regarding frequency, distribution, function, and form of definitions. A total of 315 terms were defined, indicating an average frequency of occurrence of one definition per 1 minute 55 seconds. Definitions were found to fulfil one of two main functions: signposting the logical/discourse structure of the subject/lecture, or helping to maintain comprehension as the discourse progresses. Definitions were found to often cluster together in discourse, but there was no evidence of them being more frequent at the beginning of lectures. Definitions were classified into three major types and one minor type, each of the major types being further sub- classified. Findings are reported for ordering of the semantic elements of definitions, syntactic and lexical signalling devices, and various rhetorical and paralinguistic features which accompany definitions. A final section discusses implications for pedagogy. Writing in 1972, Labov stated: There is a great deal to do in describing and analysing the patterns of use of language and dialects within specific cultures ... the way in which speakers draw upon the resources of their language to perform certain functions. (Labov 1972:184) It is now widely recognized that the research programme implied here by Labov has obvious application in the field of language teaching (see, for example, Wolfson 1981; Olshtain and Cohen 1983). Descriptive information on the form, use, distribution, and situational variation of various language functions (speech acts) provides an important source of input for syllabus design. As Olshtain and Cohen (1983:33) put it: 'in order to... plan the content of a teach- ing program, we must have a description of the speech-act sets in the target language.' This paper is presented as a further contribution to this research. Much empirical work to date has focused on a relatively restricted range of speech acts. Requests, apologies, and compliments, for example, have received a great deal of attention. These speech acts are primarily associated with the overall discourse genre of casual conversation. The present study seeks to broaden out this range to take in a speech act more associated with the field of academic discourse—that of definition. Applied Linguistics, Vol. 13, No. 2 © Oxford University Press 1992 at City University of Hong Kong on June 19, 2013 http://applij.oxfordjournals.org/ Downloaded from