This document discusses the differences between formal and informal language. Formal language is impersonal, precise, and appropriate for situations like job interviews, speeches, and academic papers. Informal language is more casual and conversational, fitting for interactions with family and friends. To sound professional, it is important to avoid certain informal constructions in written or spoken language, such as starting sentences with conjunctions, using contractions to form negatives, relying on clichés, including slang words, and choosing inappropriate word choices.