Irrational means not based on reason. The fear you know is silly and have anyway.
It describes fears, beliefs and behaviour, and an irrational fear is the standard phrase, since a phobia is irrational by definition. The word is a criticism when applied to arguments and merely descriptive when applied to feelings, which nobody chooses. Mathematics has a precise and unrelated sense, since an irrational number cannot be written as a fraction, and pi is the famous example. Rational is the opposite in both senses.
1adjectiveirrationalNot based on reason or logic.
“He has an irrational dislike of telephones.”
2adjectivemathsIn maths, unable to be expressed as a simple fraction.
“Pi is an irrational number.”
Latin
irratiōnālis
English, today
irrational
From Latin irratiōnālis, from ir- + ratiōnālis.
Etymology from Wiktionary, CC BY-SA
Practised in A Man Called Ove
First appears in chapter 20 of A Man Called Ove.
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