logic
n. uncountablen. a way of thinking that is sensible and based on good reasons. You use it to explain why one idea naturally follows another.
n. a system of reasoning or a set of principles used to determine the validity of an argument. Often refers to the internal consistency of a particular theory or chain of thought.
There is no logic in your argument.
The company followed a clear logic when they decided to lower prices to attract more customers.
While the conclusion seems radical, the internal logic of the philosopher's argument remains difficult to refute without questioning his initial premises.
From Middle English logike, from Old French and Latin logicus, from Ancient Greek λογῐκός (logĭkós).
From Middle English logik, from Old French logike, from Latin logica, from Ancient Greek λογική (logikḗ, “logic”), from feminine of λογικός (logikós, “of or pertaining to speech or reason or reasoning, rational, reasonable”), from λόγος (lógos, “speech, reason”). Displaced native Old English flitcræft (literally “art of arguing”).
Frequently used with the definite article ('the logic') when referring to a specific person's reasoning or a particular system.