an instance of a form of reasoning in which a conclusion is drawn (whether validly or not) from two given or assumed propositions (premises) that each share a term with the conclusion, and that share a common or middle term not present in the conclusion (e.g. all dogs are animals; all animals have four legs; therefore all dogs have four legs) 三段论 ■[mass noun]deductive reasoning as distinct from induction 演绎推理 logic is rules or syllogism. 逻辑是规则或是演绎推理。
late Middle English: via Old French or Latin from Greek sullogismos, from sullogizesthai, from sun- 'with' + logizesthai 'to reason' (from logos 'reasoning')