rea·son (r??z?n)n.1. a. The basis or motive for an action, decision, or conviction: There are good reasons to learn a foreign language. See Usage Notes at because, why.b. A declaration made to explain or justify action, decision, or conviction: What reasons did she give for leaving?c. A fact or cause that explains why something exists or has occurred: The reason for the building’s collapse is unknown.d. Logic A premise, usually the minor premise, of an argument.2. a. The capacity for logical, rational, and analytic thought; intelligence: “Most of us would like to believe that when we say something is right or wrong, we are using our powers of reason alone” (Carl Zimmer).b. The limit of what is reasonable: “It is a curious thing that, when a man hates or loves beyond reason, he is ready to go beyond reason to gratify his feelings” (Rudyard Kipling).c. A normal mental state; sanity: He has lost his reason.v. rea·soned, rea·son·ing, rea·sons v.tr.1. To determine or conclude by logical thinking: The doctor reasoned that the patient had a virus.2. To persuade or dissuade (someone) with reasons: “You boast … of having reasoned him out of his absurd romance” (William Makepeace Thackeray).v.intr.1. To use the faculty of reason; think logically: What would lead you to reason so?2. To talk or argue logically and persuasively: tried to reason with her son to eat a good breakfast.3. Obsolete To engage in conversation or discussion.Idioms: by reason of Because of. in reason With good sense or justification; reasonably. within reason Within the bounds of good sense or practicality. with reason With good cause; justifiably.[Middle English resoun, from Old French raison, from Latin rati?, rati?n-, from ratus, past participle of r?r?, to consider, think; see ar- in Indo-European roots.]rea?son·er n.Synonyms: reason, intuition, understanding, judgment These nouns refer to the intellectual faculty by which humans seek or attain knowledge or truth. Reason is the power to think rationally and logically and to draw inferences: “Mere reason is insufficient to convince us of its [the Christian religion’s] veracity” (David Hume). Intuition is perception or comprehension, as of truths or facts, without the use of the rational process: I trust my intuitions when it comes to assessing someone’s character. Understanding is the faculty by which one understands, often together with the resulting comprehension: “The greatest dangers to liberty lurk in insidious encroachment by men of zeal, well-meaning but without understanding” (Louis D. Brandeis). Judgment is the ability to assess situations or circumstances and draw sound conclusions: “At twenty years of age, the will reigns; at thirty, the wit; and at forty, the judgment” (Benjamin Franklin). See Also Synonyms at cause, think.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.reason (?ri?z?n) n1. the faculty of rational argument, deduction, judgment, etc2. sound mind; sanity3. a cause or motive, as for a belief, action, etc4. an argument in favour of or a justification for something5. (Philosophy) philosophy the intellect regarded as a source of knowledge, as contrasted with experience6. (Logic) logic grounds for a belief; a premise of an argument supporting that belief7. by reason of because of8. in reason within reason within moderate or justifiable bounds9. it stands to reason it is logical or obvious: it stands to reason that he will lose. 10. listen to reason to be persuaded peaceably11. (Government, Politics & Diplomacy) reasons of State political justifications for an immoral actvb12. (when tr, takes a clause as object) to think logically or draw (logical conclusions) from facts or premises13. (usually foll by: with) to urge or seek to persuade by reasoning14. (often foll by: out) to work out or resolve (a problem) by reasoning[C13: from Old French reisun, from Latin rati? reckoning, from r?r? to think] ?reasoner nUsage: The expression the reason is because? should be avoided. Instead one should say either this is because? or the reason is that?Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014rea?son (?ri z?n) n. 1. a basis or cause, as for some belief, action, fact, or event. 2. a statement presented in justification or explanation of a belief or action. 3. the mental powers concerned with forming conclusions, judgments, or inferences. 4. sound judgment; good sense. 5. normal or sound powers of mind; sanity. 6. Logic. a premise of an argument. 7. Philos. a. the faculty or power of acquiring intellectual knowledge, either by direct understanding of first principles or by argument. b. the power of intelligent and dispassionate thought, or of conduct influenced by such thought. v.i. 8. to think or argue in a logical manner. 9. to form conclusions, judgments, or inferences from facts or premises. 10. to urge reasons that should determine belief or action. v.t. 11. to think through logically, as a problem (often fol. by out). 12. to conclude or infer. 13. to convince, persuade, etc., by reasoning. 14. to support with reasons. Idioms: 1. by reason of, on account of; because of. 2. in or within reason, in accord with reason; justifiable. 3. with reason, with ample justification; fittingly. [1175?1225; Middle English resoun, reisun (n.) The reason for something is the fact or situation which explains why it happens, exists, or is done.Be Careful!Don’t use any preposition except for after reason in sentences like these.You can talk about a person’s reason for doing something.You can also talk about the reason why something happens or is done.However, if you are actually stating the reason, don’t use ‘why’. Instead you use a that-clause.Note that the second clause in these sentences is also a that-clause. Instead of a that-clause, some speakers use a clause beginning with because.This use of because is fairly common in spoken and informal English. However, some people think that it is incorrect, and you should avoid it in formal English.