Definition

1. Adjective:

   • Based on or using reason and logic: Describes thoughts, decisions, or actions that are guided by clear, sensible thinking rather than emotion.
   • Sane or reasonable: Describes a person who is thinking clearly and sensibly.
   • (Mathematics) Expressible as a ratio of integers: Describes a number that can be written as a fraction where both the numerator and denominator are integers, and the denominator is not zero.

2. Noun:

   • A rational number: In mathematics, a number that can be expressed as a quotient or fraction of two integers.

Usage Examples

• Adjective:

  • In a crisis, it's important to make rational decisions. (Here, "rational" describes decisions based on logic.)
  • After a good night's sleep, she felt more rational and could assess the problem calmly. (Here, "rational" describes a state of clear, sensible thinking.)
  • The number 0.75 is a rational number because it can be written as 3/4. (Here, "rational" is a mathematical term.)

• Noun:

  • The set of rationals is denoted by the letter Q. (Here, "rationals" is a plural noun referring to rational numbers.)

Advanced Usage

• "Perfectly rational": Completely logical and reasonable.

  • His fear, though intense, was a perfectly rational response to the danger.

• "Rational basis": A foundation in logic or reason.

  • The policy must have a rational basis to be considered valid.

• "Boundedly rational": A concept in economics describing decision-making that is intendedly rational but limited by available information and cognitive capacity.

  • In the real world, consumers are often boundedly rational.

Variants and Related Words

• Rationality (n): The quality of being based on reason.

  • The debate was praised for its high level of rationality.

• Rationalize (v): To attempt to explain or justify behavior with logical reasons, even if these are not the true motives.

  • He tried to rationalize his impulsive purchase.

• Irrational (adj): The opposite of rational; not based on reason or logic.

  • An irrational fear of spiders is called arachnophobia.

Synonyms

• Logical: Following the rules of formal logic.
• Reasonable: Having sound judgment; fair and sensible.
• Sensible: Showing good sense or judgment; practical.
• Coherent: Logical and consistent.

Antonyms

• Irrational: Not logical or reasonable.
• Emotional: Based on feelings rather than logic.
• Illogical: Lacking sense or sound reasoning.

Related Phrases and Idioms

• "Rational actor": A term in social science for an individual who makes decisions to achieve optimal outcomes based on available information.

  • The model assumes every consumer is a rational actor.

• "Rational choice": A decision-making paradigm that selects the best option among alternatives based on calculated utility.

  • Voting is often studied through the lens of rational choice theory.

Adjective

1. having its source in or being guided by the intellect (as distinguished from experience or emotion)
   • a rational analysis
2. capable of being expressed as a quotient of integers
   • rational numbers
3. of or associated with or requiring the use of the mind
   • intellectual problems
   • the triumph of the rational over the animal side of man
4. consistent with or based on or using reason
   • rational behavior
   • a process of rational inference
   • rational thought

Noun

1. an integer or a fraction