Merriam-Webster Collegiate Dictionary - logic

 noun  Etymology: Middle English logik, from Anglo-French, from Latin ~a, from Greek logike, from feminine of logikos of reason, from logos reason — more at legend  Date: 12th century  1.  a.  (1) a science that deals with the principles and criteria of validity of inference and demonstration ; the science of the formal principles of reasoning  (2) a branch or variety of ~ modal ~ Boolean ~  (3) a branch of semiotic; especially syntactics  (4) the formal principles of a branch of knowledge  b.  (1) a particular mode of reasoning viewed as valid or faulty  (2) relevance, propriety  c. interrelation or sequence of facts or events when seen as inevitable or predictable  d. the arrangement of circuit elements (as in a computer) needed for computation; also the circuits themselves  2. something that forces a decision apart from or in opposition to reason the ~ of war  • ~ian noun