logic

Etymology 1

From Middle English logike, from Old French and Latin logicus, from Ancient Greek λογῐκός (logikós).

adj

1. logical

Etymology 2

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”).

noun

1. (uncountable) A method of human thought that involves thinking in a linear, step-by-step manner about how a problem can be solved. Logic is the basis of many principles including the scientific method.
2. (philosophy, logic) The study of the principles and criteria of valid inference and demonstration.
   An old tradition has it that there are two branches of logic: deductive logic and inductive logic. More recently, the differences between these disciplines have become so marked that most people nowadays use "logic" to mean deductive logic, reserving terms like "confirmation theory" for at least some of what used to be called inductive logic. I shall follow the more recent practice, and shall construe "philosophy of logic" as "philosophy of deductive logic". 2001, Mark Sainsbury, Logical Forms - An Introduction to Philosophical Logic, Second Edition, Blackwell Publishing, page 9
3. (uncountable, mathematics) The mathematical study of relationships between rigorously defined concepts and of mathematical proof of statements.
4. (countable, mathematics) A formal or informal language together with a deductive system or a model-theoretic semantics.
5. (uncountable) Any system of thought, whether rigorous and productive or not, especially one associated with a particular person.
   It's hard to work out his system of logic.
   This hypothesis goes by many names, including group resistence, the threshold effect, and the gender paradox. Because the hypothesis holds such wide appeal, it is worth revisiting the logic behind it. The hypothesis is built on the factual observation that fewer females than males act antisocially. 27 September 2001, Terrie E. Moffitt, Avshalom Caspi, Michael Rutter, Phil A. Silva, Sex Differences in Antisocial Behaviour: Conduct Disorder, Delinquency, and Violence in the Dunedin Longitudinal Study, Cambridge University Press, page 151
   "It's not a matter of opinion that she wasn't anywhere near her husband when somebody shoved a needle in him," I said, miffed. "I would have seen her." "By that logic, nobody did it because you didn't see anybody." 2020, Dan Andriacco, Murderers' Row
6. (uncountable) The part of a system (usually electronic) that performs the boolean logic operations, short for logic gates or logic circuit.
   Fred is designing the logic for the new controller.

verb

1. (intransitive, derogatory) To engage in excessive or inappropriate application of logic.
   Nay, is not the author himself "logicking" against logic, from the beginning of his book to the end ? 1884, Orestes Augustus Brownson, Controversy, page 21
2. (transitive) To apply logical reasoning to.
   He logicked that one out. He snuck into Haiti and scored herbs to rev him and calm him. 2010, James Ellroy, Blood's a Rover, page 90
3. (transitive) To overcome by logical argument.
   If things had gone as usual this night, if Kit had not logicked her into agreement, then she probably would have opened the door tonight. 2010, Jade Lee, Wicked Surrender