irrational
Not in accordance with reason or logic; inaccessible to, or contradicting, rational understanding.
EXAMPLE
Seine Angst vor Spinnen ist völlig irrational.
His fear of spiders is completely irrational.
irrational
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Meanings
irrational
In mathematics, the property of a number that cannot be represented as a fraction of two whole numbers.
EXAMPLE
Die Kreiszahl Pi ist eine bekannte irrationale Zahl.
The number pi is a well-known irrational number.
Usage tips
Word structure
The word consists of the prefix 'ir-' and the word 'rational'. The prefix 'ir-' is a variant of 'in-' and means 'not'. So 'irrational' literally means 'not rational' or 'unreasonable'.
EXAMPLE
Es ist irrational, ohne Jacke bei Kälte nach draußen zu gehen.
It is irrational to go outside in the cold without a jacket.
Context clues
You can easily recognize the meaning from the context. If people are talking about feelings, behavior, or decisions, the general meaning 'unreasonable' is meant. In the context of mathematics, numbers, or formulas, the specific mathematical meaning is meant.
EXAMPLE
Ihre plötzliche Wut war völlig irrational.
Her sudden anger was completely irrational.
Typical collocations
In the general meaning, 'irrational' is often connected with human reactions and thoughts. Common combinations are 'eine irrationale Angst' (an irrational fear), 'irrationales Verhalten' (irrational behavior), or 'eine irrationale Entscheidung' (an irrational decision).
EXAMPLE
Er hat eine irrationale Angst vor geschlossenen Räumen.
He has an irrational fear of enclosed spaces.
Mathematical use
In mathematics, this adjective is used almost exclusively in the fixed expression 'irrationale Zahl' (irrational number). It describes numbers that cannot be represented as a fraction.
EXAMPLE
Im Unterricht haben wir über rationale und irrationale Zahlen gesprochen.
In class, we talked about rational and irrational numbers.
Compare with
irrational vs unlogisch
illogical
Unlogisch is appropriate when a line of thought contradicts the rules of logic or contains a contradiction. Irrational is broader and describes something that cannot be understood through reason. An irrational thought can therefore also be illogical, but it does not have to contain a clear logical error.
irrational
Der Gedankengang wirkt irrational, weil er trotz aller Fakten nur von Angst bestimmt wird.
The line of reasoning seems irrational because, despite all the facts, it is driven solely by fear.
unlogisch
Der Gedankengang ist unlogisch, weil sich seine beiden Aussagen widersprechen.
The line of reasoning is illogical because its two statements contradict each other.
In real life
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