# rational

/ˈɹæʃənəɫ/ (US) · /ɹˈæʃənəl/ (UK)

Source: https://englishreference.com/word/rational
Updated: 2026-06-19

## Senses

### 1. logical and sensible

adjective · CEFR B2

based on clear thinking and facts rather than emotions.

For teachers: based on or in accordance with reason or logic; exhibiting intellectual soundness.

- We need to have a rational discussion about the budget instead of getting angry.
- The committee attempted to reach a rational conclusion by weighing the statistical evidence against the projected long-term costs.

### 2. capable of reasoning

adjective · CEFR C1 · Academic

having the ability to think, understand, and use logic.

For teachers: possessing the capacity for reason; often used to distinguish humans from other animals in philosophical contexts.

- Aristotle famously described humans as rational animals.
- The debate centered on whether artificial intelligence could ever truly be considered a rational agent with its own intent.

### 3. math/ratios

adjective · CEFR B2 · Technical

describing a number that can be shown as a simple fraction.

For teachers: relating to or being a number that can be expressed as the quotient of two integers.

- The number 0.75 is rational because it can be written as three-quarters.
- The proof demonstrates that while the square root of two is irrational, its square is a rational integer.

### 4. a rational number

noun · CEFR C1 · Technical

a number that can be expressed as one integer divided by another.

For teachers: a rational number; any value that can be represented as a ratio of two integers where the denominator is not zero.

- In this equation, x must be a rational rather than an irrational number.
- The set of rationals is dense, meaning that between any two distinct rational numbers, there exists another rational.

## Examples

- He made a rational decision to save his money.
- In a crisis, it is difficult to remain rational and avoid making decisions based on fear.
- The economist argued that while individuals aim to be rational, their choices are often limited by the information available to them at the time.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.