ir·ra·tio·nal /ɪˈræʃ(ə)nəl, ˌɪ(r)-/
 無理數(a.)無理性的,不合理的
 ir·ra·tio·nal /(ˈ)ɪrˈ(r)æʃnəl, ənḷ/ 形容詞
 adj.無理性的,不合理的
 ir·ra·tion·al a.
 1. Not rational; void of reason or understanding; as, brutes are irrational animals.
 2. Not according to reason; having no rational basis; clearly contrary to reason; easily disproved by reasoning; absurd; -- of assertions and beliefs. Hence, of actions: foolish; unreasonable.
    It seemed utterly irrational any longer to maintain it.   --I. Taylor.
 3. Math. Not capable of being exactly expressed by an integral number, nor by a ratio of integral numbers; surd; -- said especially of roots. See Surd.
 Syn: -- Absurd; foolish; preposterous; unreasonable; senseless. See Absurd.
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 irrational
      adj 1: not consistent with or using reason; "irrational fears";
             "irrational animals" [ant: rational]
      2: real but not expressible as the quotient of two integers;
         "irrational numbers" [ant: rational]