A substantially revised edition of Huddleston's contribution to Sentence and Clause in Scientific English, the final report of a research project into the linguistic properties of scientific English carried out at University College London in 1964-7. The book has two complementary aims: to analyse certain areas of the grammar of 'common-core' English - the grammar that is common to all varieties of the language - and to apply this analysis to a selective grammatical description of a corpus of some 135,000 words of written scientific English. The theoretical framework underlying the description is that of transformational grammar but the author also draws heavily on M. A. K. Halliday's work on English grammar. Full details of the corpus are given in the appendix. The texts are arranged in three levels, high, middle and low, according to the audience addressed by the author - scholarly, student and general/popular.