THE DESCRIPTIVE SCIENCE OF LINGUISTICS AND THE SKILL OF WRITTEN COMPOSITION MEET IN THE "SENTENCE," AND THE INFORMATION WHICH LINGUISTICS PROVIDES ON SENTENCE STRUCTURE CAN AID THE TEACHER OF COMPOSITION. ALTHOUGH TRADITIONAL GRAMMAR DOES NOT IMPROVE A STUDENT'S WRITING, CONSTITUENT GRAMMAR AND TRANSFORMATIONAL GRAMMAR, BY PRESENTING METHODS OF ANALYZING AND ORGANIZING SENTENCES, ENABLE THE STUDENT TO FAMILIARIZE HIMSELF WITH THE BASIC FORMS AND ELEMENTS OF THE SENTENCE. THROUGH PRACTICE, A STUDENT'S "REPLACEMENT POTENTIAL" (THE RANGE OF POSSIBILITIES HE HAS AVAILABLE FOR A GIVEN SLOT IN A SENTENCE) IS INCREASED, AND HE LEARNS THE MANIPULATION AND GROUPING OF SENTENCE PARTS. AS HIS OBJECTIVE APPRECIATION OF SENTENCE STRUCTURE AND ITS VARIATIONS GROWS, HE ACQUIRES A CONCEPT OF CONSTRUCTION WHICH CAN BE APPLIED TO GROUPS OF SENTENCES AS WELL AS GROUPS OF WORDS, AND CONSEQUENTLY IS BETTER ABLE TO WRITE UNIFIED PARAGRAPHS AND PAPERS. THUS, ALTHOUGH LINGUISTICS PROPER IS NOT CAPABLE OF DEALING WITH UNITS OF COMPOSITION LARGER THAN THE SENTENCE, THE APPROACHES DEVELOPED BY LINGUISTS FOR STUDYING SENTENCES CAN AID THE STUDENT OF COMPOSITION TO IMPROVE HIS WRITING SKILLS. (THIS ARTICLE APPEARED IN "LANGUAGE, LINGUISTICS, AND SCHOOL PROGRAMS, PROCEEDINGS OF THE SPRING INSTITUTES, 1963." CHAMPAIGN, ILL., NCTE, 1963.) (LH)