Abstract
Students usually compose adequate descriptive abstracts, but many confuse summary abstracts with short paraphrases or descriptive abstracts. Textbooks define a summary abstract ambiguously, as a “mini-paper” and/or as a mere statement of an article's topic and conclusions; most textbooks maintain the conceptual distinction between summary and descriptive abstracts even though differences between the two types are blurred in practice. These irregularities are accounted for by a hypothesis: in all levels of discourse, from sentences to extended texts, general and specific components conserve the “shape” of information. Intermediate discourse components (e.g., sentential tense, the syllogistic middle term, or the body of a text) may be deleted to create a smaller equivalent discourse structure. The two polar abstract types represent polar (general vs. specific) text components. Common abstracting errors arise from two sources: failure to distinguish between an abstract as “mini-paper” and a short paraphrase from the body of a long text, but also failure to distinguish between general topical information and the specific claims of a text, attributed to students' usual lack of acquaintance with other literature on a topic, besides the article they attempt to abstract.