A rational motive for a belief or action:
— The reason that war was declared.

synonym: ground.

Roget 153: cause, origin, source, principle, element; occasioner^†, prime mover, primum mobile [Lat.]; vera causa [Lat.]; author etc. (producer) 164; mainspring; agent; leaven; groundwork, foundation etc. (support) 215.    spring, fountain, well, font; fountainhead, spring head, wellhead; fons et origo [Lat.], genesis; descent etc. (paternity) 166; remote cause; influence.    pivot, hinge, turning point, lever, crux, fulcrum; key; proximate cause, causa causans [Lat.]; straw that breaks the camel's back.    ground; reason, reason why; why and wherefore, rationale, occasion, derivation; final cause etc. (intention) 620; les dessous des cartes [Fr.]; undercurrents.    rudiment.    egg, germ, embryo, bud, root, radix radical, etymon, nucleus, seed, stem, stock, stirps, trunk, tap-root, gemmule^†, radicle, semen, sperm.    nest, cradle, nursery, womb, nidus, birthplace, hotbed.    causality, causation; origination; production etc. 161.    ... show more

Roget 615: motive, springs of action, wellsprings of action.    reason, ground, call, principle; by end, by purpose; mainspring, primum mobile [Lat.], keystone; the why and the wherefore; pro and con, reason why; secret motive, arriere pensee [Fr.]; intention etc. 620.    inducement, consideration; attraction; loadstone; magnet, magnetism, magnetic force; allectation^†, allective^†; temptation, enticement, agacerie^†, allurement, witchery; bewitchment, bewitchery; charm; spell etc. 993; fascination, blandishment, cajolery; seduction, seducement; honeyed words, voice of the tempter, song of the Sirens forbidden fruit, golden apple.    persuasibility^†, persuasibleness^†; attractability^†; impressibility, susceptibility; softness; persuasiveness, attractiveness; tantalization^†.    influence, prompting, dictate, instance; impulse, impulsion; incitement, incitation; press, instigation; provocation etc. (excitation of feeling) 824; inspiration; persuasion, suasion; encouragement, advocacy; exhortation; advice etc. 695; solicitation etc. (request) 765; lobbyism; pull [Slang].    incentive, stimulus, spur, fillip, whip, goad, ankus^†, rowel, provocative, whet, dram.    bribe, lure; decoy, decoy duck; bait, trail of a red herring; bribery and corruption; sop, sop for Cerberus.    prompter, tempter; seducer, seductor^†; instigator, firebrand, incendiary; Siren, Circe; agent provocateur; lobbyist.    ... show more

Dutch: reden, afweging, beweeggrond, beweegreden, considerans, consideratie, drijfveer, grond, motief, motivatie, overweging, ratio ... show more
Polish: przyczyna, źródło, racja, motyw, pobudka, powód

An explanation of the cause of some phenomenon.

The capacity for rational thought or inference or discrimination:
— We are told that man is endowed with reason and capable of distinguishing good from evil.

synonyms: intellect, understanding.

Roget 450: intellect, mind, understanding, reason, thinking principle; rationality; cogitative faculties, cognitive faculties, discursive faculties, reasoning faculties, intellectual faculties; faculties, senses, consciousness, observation, percipience, intelligence, intellection, intuition, association of ideas, instinct, conception, judgment, wits, parts, capacity, intellectuality, genius; brains, cognitive powers, intellectual powers; wit etc. 498; ability etc. (skill) 698; wisdom etc. 498; Vernunft [G.], Verstand [G.].    soul, spirit, ghost, inner man, heart, breast, bosom, penetralia mentis [Lat.], divina particula aurae [Lat.], heart's core; the Absolute, psyche, subliminal consciousness, supreme principle.    brain, organ of thought, seat of thought; sensorium^†, sensory; head, headpiece; pate, noddle^†, noggin, skull, scull, pericranium [Med.], cerebrum, cranium, brainpan^†, sconce, upper story.    [in computers] [Comp.] central processing unit, CPU; arithmetic and logical unit, ALU.    [Science of mind] metaphysics; psychics, psychology; ideology; mental philosophy, moral philosophy; philosophy of the mind; pneumatology^†, phrenology; craniology [Med.], cranioscopy [Med.].    ideality, idealism; transcendentalism, spiritualism; immateriality etc. 317; universal concept, universal conception.    metaphysician, psychologist etc. ... show more

Dutch: denkvermogen, geestvermogen, hersens, rede, verstand
Polish: rozsądek, rozsądność, rozum, logika

The state of having good sense and sound judgment:
— He had to rely less on reason than on rousing their emotions.

synonyms: rationality, reasonableness.

Roget 498: intelligence, capacity, comprehension, understanding; cuteness, sabe [U.S.], savvy [U.S.]; intellect etc. 450; nous [Fr.], parts, sagacity, mother wit, wit, esprit, gumption, quick parts, grasp of intellect; acuteness etc. adj.; acumen, subtlety, penetration, perspicacy^†, perspicacity; discernment, due sense of, good judgment; discrimination etc. 465; cunning etc. 702; refinement etc. (taste) 850.    head, brains, headpiece, upper story, long head; eagle eye, eagle-glance; eye of a lynx, eye of a hawk.    wisdom, sapience, sense; good sense, common sense, horse sense [U.S.], plain sense; rationality, reason; reasonableness etc. adj.; judgment; solidity, depth, profundity, caliber; enlarged views; reach of thought, compass of thought; enlargement of mind.    genius, inspiration, geist [G.], fire of genius, heaven-born genius, soul; talent etc. (aptitude) 698.    [Wisdom in action] prudence etc. 864; vigilance etc. 459; tact etc. 698; foresight etc. 510; sobriety, self-possession, aplomb, ballast.    a bright thought, not a bad idea.    Solomon-like wisdom.    ... show more

Dutch: redelijkheid
Polish: racjonalność

A justification for something existing or happening:
— They had good reason to rejoice.

synonyms: cause, grounds.

Dutch: veroorzaken

A fact that logically justifies some premise or conclusion.

Dutch: doordenken, argumenteren, overleggen, overdenken, overwegen, redeneren

Decide by reasoning; draw or come to a conclusion:
— We reasoned that it was cheaper to rent than to buy a house.

synonyms: conclude, reason out.

Dutch: afleiden, besluiten, concluderen, opmaken

Present reasons and arguments.

synonym: argue.

Roget 476: reason, argue, discuss, debate, dispute, wrangle^†, argufy^†, bandy words, bandy arguments; chop logic; hold an argument, carry on an argument; controvert etc. (deny) 536; canvass; comment upon, moralize upon; spiritualize; consider etc. (examine) 461.    open a discussion, open a case; try conclusions; join issue, be at issue; moot; come to the point; stir a question, agitate a question, ventilate a question, torture a question; take up a side, take up a case.    contend, take one's stand upon, insist, lay stress on; infer etc. 480.    follow from etc. (demonstration) 478.    ... show more

Dutch: argumenteren, baseren, beargumenteren, funderen, gronden, onderbouwen

Think logically.