This issue contains two articles in Spanish and three in English on the following topics: the practical presentation of English for Special Purposes (ESP) materials in science programs at the National University of Trujillo, "notional syllabus" and "discourse analysis" in relation to ESP materials, extra-linguistic principles in explaining language facts, diphthongation in "Kechwa de Ancash-Huaylas," and a typology of language situations. The first article is a discussion of some aspects of the practical classroom presentation of texts in scientific English using recently published textbooks. The second article is a discussion of terms: notional syllabus refers to the organization of a syllabus according to semantic expression. Discourse analysis refers to the informational coherence of texts, and the markers used to point the way to understanding such texts. In the third paper, some of the extra-linguistic principles related to language use that enable human beings to interact socially are discussed. The distinctive features of one of the dialects in the Quechua group of dialects are analyzed in the fourth article. Thirty types of communication situations involving interaction of the five factors: "speaker, listener, channel, code and information" are discussed and classified in the last article. (AMH)