adj

irrational

ih-RASH-nuhl

adj

Not based on logic or reason; unfounded or nonsensical.

"He had an irrational fear of elevators."

"Her boss made an irrational decision that hurt the whole team."

In mathematics, describing a real number that cannot be written as a fraction of two whole numbers.

"Pi is a famous example of an irrational number."

How to Use Irrational

Learner’s notes

In plain EnglishNot making logical sense — or, in math, a number that goes on forever without repeating and can't be written as a simple fraction.

Common pairings

irrational fear irrational number irrational behavior

more irrational comparative, irrationals plural, most irrational superlative

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Can you complete this real example?

He had an _____ fear of elevators.

From Latin irratiōnālis, from ir- ("not") plus ratiōnālis ("rational").

coronal rational diagonal personal seasonal national optional regional hormonal fictional emotional impersonal