Irrational
/ɪˈræʃənəl/noun
Not based on reason or logic; also, in mathematics, a number that cannot be expressed as a ratio of two integers.
Did you know?The mathematical sense of irrational comes from the same Latin root as ratio, showing that ancient ideas of “reason” and “calculation” were tightly fused long before modern math.
Etymological Timeline
Latin
Latin
irrationalis
“not reasonable; not proportioned”
Late Latin
Latin
irrationalis
“unreasonable, without reason”
Old French
Old French
irracionel
“unreasonable; lacking logic”
14th Century
English
irracional / irrational
“unreasonable; contrary to reason”
17th Century
English
irrational
“in mathematics, not expressible as a ratio of integers”
Modern English
English
irrational
“not based on reason; not a rational number”