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  1. the science that investigates the principles governing correct or reliable inference.
  2. a particular method of reasoning or argumentation: We were unable to follow his logic.
  3. the system or principles of reasoning applicable to any branch of knowledge or study.
  4. reason or sound judgment, as in utterances or actions: There wasn't much logic in her move.
  5. convincing forcefulness; inexorable truth or persuasiveness: the irresistible logic of the facts.
  6. Computers. logic circuit.

Origin of logic

1325–75; Middle English logik < Latin logica, noun use of neuter plural (in ML taken as feminine singular) of Greek logikós of speech or reason. See logo-, -ic
Related formslog·ic·less, adjectivenon·log·ic, noun

Synonyms for logic

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  1. a combining form used in the formation of adjectives corresponding to nouns ending in -logy: analogic.

Origin of -logic

< Greek -logikós. See logic
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for logic


  1. the branch of philosophy concerned with analysing the patterns of reasoning by which a conclusion is properly drawn from a set of premises, without reference to meaning or contextSee also formal logic, deduction (def. 4), induction (def. 4)
  2. any particular formal system in which are defined axioms and rules of inferenceCompare formal system, formal language
  3. the system and principles of reasoning used in a specific field of study
  4. a particular method of argument or reasoning
  5. force or effectiveness in argument or dispute
  6. reasoned thought or argument, as distinguished from irrationality
  7. the relationship and interdependence of a series of events, facts, etc
  8. chop logic to use excessively subtle or involved logic or argument
  9. electronics computing
    1. the principles underlying the units in a computer system that perform arithmetical and logical operationsSee also logic circuit
    2. (as modifier)a logic element

Word Origin for logic

C14: from Old French logique from Medieval Latin logica (neuter plural, treated in Medieval Latin as feminine singular), from Greek logikos concerning speech or reasoning
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for logic

mid-14c., "branch of philosophy that treats of forms of thinking," from Old French logique (13c.), from Latin (ars) logica, from Greek logike (techne) "reasoning (art)," from fem. of logikos "pertaining to speaking or reasoning," from logos "reason, idea, word" (see logos). Meaning "logical argumentation" is from c.1600.

Online Etymology Dictionary, © 2010 Douglas Harper

logic in Science


  1. The study of the principles of reasoning, especially of the structure of propositions as distinguished from their content and of method and validity in deductive reasoning.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

logic in Culture


The branch of philosophy dealing with the principles of reasoning. Classical logic, as taught in ancient Greece and Rome, systematized rules for deduction. The modern scientific and philosophical logic of deduction has become closely allied to mathematics, especially in showing how the foundations of mathematics lie in logic.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.