The rationale for something is the basic or underlying reason or explanation for it. This noun (pronounced "rash-uh-NAL") is usually used in the singular: What was the rationale behind his decision to quit?

The related adjective rational means "based on facts or reason" or "having the ability to think clearly." An example of a rational rationale? You add extra baking soda to pancake batter under the rationale that if you want them to be fluffier, you need more rising agent. Rationale is from Latin, from rationalis "relating to reason," from ratio "calculation, reason," from rērī "to consider, think."

Definitions of rationale
  1. noun
    (law) an explanation of the fundamental reasons (especially an explanation of the working of some device in terms of laws of nature)
    “the rationale for capital punishment”
    synonyms: principle
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    a rationale for dialectical materialism based on change through the conflict of opposing forces
    type of:
    thought that makes something comprehensible
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