1. a number, for example π or the square root of 2, that cannot be expressed as the ratio of two whole numbers
   Word Originmid 16th cent.: from Latin surdus ‘deaf, mute’; as a mathematical term, translating Greek (Euclid) alogos ‘irrational, speechless’, apparently via Arabic jid̲r asÌ£amm, literally ‘deaf root’.

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