What does irrationally mean?
Irrationality means the absence of reason, logic, or sound judgment, and irrationally describes actions or attitudes conducted in that way. The word is commonly used for decisions that ignore relevant facts, emotional reactions that override self-control, and behavior that seems excessive or impossible to justify. For example, someone might act irrationally by refusing a reasonable offer after becoming angry, or by making a sudden choice without considering its consequences. Although the word is related to the mathematical idea of irrational numbers, its everyday use is primarily about thinking and conduct rather than arithmetic. It is more formal and more evaluative than simply saying that a person is “emotional” or “impulsive,” and it often implies that the behavior can be seen as mistaken or out of proportion. The opposite is rationally, meaning in accordance with reason and careful judgment.
adverbIn a way that is not based on reason, logic, or sound judgment; without rational control.
- In a way that is not based on reason or sound judgment.
- Without the control or moderation that reason would normally provide.
"She responded irrationally to the criticism and made a decision she later regretted."
"The decision was made irrationally, without considering the consequences."
"He reacted irrationally when he heard the news and said things he could not take back."
Irrationally captures a double idea: behavior that ignores logic and conduct that goes beyond what reason could justify.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does irrationally come from?
The word comes from the Latin adjective irrationalis, meaning “not rational” or “without reason.” It is formed from the root ratio, a Latin noun associated with calculation, proportion, and reason, together with the negative prefix in- and the adjective suffix -alis. The English adjective irrational developed from this Latin word, while irrationally is the adverb derived from it.
How irrationally is actually used
The adverb is formal and generally critical: it describes behavior, decisions, or responses that lack logic or reasonable restraint. In everyday use, it often suggests emotional, impulsive, or excessive conduct rather than a merely mistaken judgment.
Easily confused with irrationally
Irrationally means without reason or logical judgment, whereas rationally means according to reason and sound judgment.