irrational

/ɪˈræʃənl/ (bre, ipa) · /ɪˈræʃənl/ (ame, ipa) · /i-ˈra-sh(ə-)nəl ˌi(r)-/ (ame, mw)

irrational — 形容詞

  • irrationalpositive
  • more irrationalcomparative
  • most irrationalsuperlative

1. used to describe thoughts, feelings, or actions that are based on strong emotion

1.形容詞B2
釋義

不理性的

缺乏理性；情緒化的

used to describe thoughts, feelings, or actions that are based on strong emotions such as fear or anger rather than on clear reasoning or facts.

例句

Theo's fear of spiders is completely irrational, since none in his country are dangerous.

Theo 對蜘蛛的恐懼完全不理性，因為他的國家沒有危險的蜘蛛。

collocation: completely irrational

The committee made an irrational decision when they refused to look at the new evidence.

委員會拒絕查看新證據，做出了一個不理性的決定。

collocation: irrational decision

同義詞
  • unreasonable

    broader; can describe a person, demand, or situation that is not fair or sensible

  • illogical

    focuses on flaws in reasoning rather than emotion-driven behaviour

  • absurd

    more extreme; describes something so unreasonable it is ridiculous

  • groundless

    specifically about fears or beliefs that have no basis in fact

反義詞
  • rational

    based on clear reason and good judgment

  • logical

    following the rules of correct reasoning

  • reasonable

    fair, sensible, and based on facts

文法句型

it is irrational to + infinitive

an irrational + noun

irrational that + clause

用法筆記

Frequently describes emotions or behaviours that the person themselves may recognise as unreasonable (e.g., irrational fear, irrational jealousy). Subject can be a person, an emotion, or a decision.

常見錯誤

❌The mathematician found an irrational error in the proof.
✅The mathematician found a logical error in the proof.
💡'irrational' describes emotion-driven behaviour, not mistakes in formal reasoning; use 'logical error' for math or argument flaws.
❌She made an irrational choice between two equally priced items.
✅She made an arbitrary choice between two equally priced items.
💡'arbitrary' means no clear reason at all; 'irrational' means acting against reason, usually driven by emotion.

2. describes a number you cannot write exactly in the form a/b where a and b are wh

2.形容詞B2
釋義

無理數的

無法以整數比表示的

describes a number you cannot write exactly in the form a/b where a and b are whole numbers — for example, the square root of 2 or pi.

例句

The square root of two is itself irrational — its digits never form a repeating pattern.

二的平方根是無理數，其小數位數永遠不會重複。

example: square root of two as irrational number

Students learn about irrational numbers when they study geometry in high school.

學生在高中學習幾何時會學到無理數。

同義詞
  • non-terminating

    describes a decimal that continues without end, a property shared by some irrational numbers

  • non-repeating

    describes a decimal with no repeating pattern, a defining feature of irrational numbers

反義詞
  • rational

    can be expressed as a fraction of two whole numbers

文法句型

irrational + number/noun

用法筆記

Used only in mathematical contexts to classify numbers such as √2, √3, and π. In everyday language, the 'NOT LOGICAL' sense (sense 1) is the one people encounter far more often.

常見錯誤

❌The fraction one third is irrational.
✅The fraction one third is rational
💡it can be written as 1/3.' — a rational number CAN be written as a fraction; 1/3 = 0.333... repeating, so it is rational, not irrational.

irrational — 名詞