rational
gb/ɹˈæʃənəl/ us/ɹˈæʃənəl/
B2
English
~ 8100
Senses
0 senses
adjective
B2
property
1
based on clear, logical reasons
Using clear thinking and good reasons, not just feelings, to decide or explain something.
Usage pattern:
a rational [decision/argument/explanation] about [something]
Common mistake:
Learners sometimes confuse "rational" (based on logic) with "rationale" (a noun meaning the reason or explanation for something). For example, "a clear rationale" is correct, not "a clear rational". Another mistake is using "rational" where "realistic" or "practical" is better, e.g. "a rational goal" vs. "a realistic goal".
Synonyms
logical (Focuses more strongly on following rules of logic and clear thinking.)
|
reasonable (Very close in meaning, but can sound slightly less formal and more about being sensible in real life.)
|
well-founded (Highlights that the decision or belief has strong reasons or evidence behind it.)
Antonyms
irrational (Describes ideas or decisions that do not follow reason or logic.)
|
emotional (In this context, emphasizes decisions guided mainly by feelings instead of careful thought.)
Collocations
rational decision
|rational argument
|rational explanation
|rational conclusion
|rational analysis
|rational choice
Themes
thinking
|communication
|work
|core_vocabulary
|education
Examples
- We need a rational plan for reducing costs without harming our staff.
- Her decision to leave was completely rational once you know all the facts.
- The lawyer presented a clear, rational argument that convinced the jury.
- Investors are looking for a rational explanation for the sudden drop in prices.
- From a rational point of view, it makes sense to wait before buying a house.
Learner examples
- He made a rational choice after thinking for a long time.
- Please give me a rational reason for changing the schedule.
- Her report is very rational and easy to follow.
- That is not a rational way to solve the problem.
- They tried to have a rational discussion about money.
adjective
B2
property
2
able to think clearly and sensibly
Able to think clearly and calmly, and not act in a crazy or wild way.
Usage pattern:
[someone] is (not) rational
Common mistake:
Learners sometimes use "rational" only for ideas, not people, and say things like "He is a reason person" instead of "He is a rational person." They may also confuse "rational" with "rationalize" (a verb meaning to invent reasons to justify something, often in a negative sense).
Synonyms
sane (Focuses more on mental health and not being mentally ill.)
|
clear-headed (Stresses being able to think clearly, especially in stressful situations.)
|
level-headed (Highlights calm and balanced judgment, especially under pressure.)
Antonyms
irrational (Describes a person who often acts or thinks without logic or good sense.)
|
crazy (Informal; suggests very unreasonable or mentally unstable behavior.)
Collocations
rational person
|rational human being
|rational mind
|rational adult
|rational agent
|rational discussion
Themes
personality
|emotions
|thinking
|health
Examples
- Try to stay rational and calm while we figure out what to do.
- She is usually very rational, even when everyone else is panicking.
- No rational person would invest all their savings in such a risky scheme.
- He was too angry to be rational about the situation.
- The therapist helped him become more rational in how he reacted to stress.
Learner examples
- Please be rational and listen to me.
- A rational person does not shout at their friends.
- He was not rational after he heard the bad news.
- When I am tired, I am less rational.
- She is very rational and does not make quick, emotional choices.
adjective
B2
property
3
moderate and not extreme
Not too big, too hard, or too strong; fair and sensible in size or level.
Usage pattern:
a rational [price/amount/expectation/demand]
Common mistake:
Learners often use only "reasonable" in this sense and may not realize that "rational" can also describe fair prices, demands, or expectations. Also, they sometimes say "rationally price" instead of "rational price"; here, "rational" is an adjective, not an adverb.
Synonyms
reasonable (The most common everyday choice; very close in meaning here.)
|
moderate (Emphasizes that something is in the middle, not too high or too low.)
Antonyms
excessive (Describes an amount or demand that is much too high.)
|
unreasonable (Covers prices, demands, or expectations that are unfair or too extreme.)
Collocations
rational price
|rational amount
|rational expectations
|rational demand
|rational level
|rational use
Themes
money
|work
|daily life
|core_vocabulary
|daily_life
Examples
- We are asking for a rational price that reflects the car’s condition.
- Employees have a rational expectation of safe working conditions.
- The judge said the company’s policy was not a rational response to the problem.
- There is no rational limit on how many emails he sends each day.
- Governments try to encourage the rational use of water in dry regions.
Learner examples
- The rent is high, but it is still rational for this area.
- We must keep our costs at a rational level.
- Parents should have rational rules for their children.
- Your request for two days off is rational.
- Her fears are rational, because the risk is real.
adjective
technical
C1
property
4
of a number, expressible as a fraction
In math, about a number that you can write as one whole number divided by another whole number, where the second number is not zero.
Usage pattern:
a rational [number/function]
Common mistake:
Learners sometimes think "rational" here means "reasonable" in the everyday sense. In math, it has a strict meaning: a number that can be written as one integer over another non-zero integer. They may also confuse "rational" with "real"; all rational numbers are real, but not all real numbers are rational.
Synonyms
non-irrational (Technical contrast term; means a number is not irrational, but "rational" is the standard precise term.)
Antonyms
irrational (In mathematics, describes numbers that cannot be written as a ratio of integers, such as π or √2.)
Collocations
rational number
|rational function
|rational coefficient
|rational fraction
|rational root
|rational expression
Themes
math
|science
|education
Examples
- Every integer is also a rational number.
- The teacher asked the students to decide whether each given value was rational or irrational.
- The solution to the equation is not a rational number.
- Rational coefficients make the polynomial easier to factor.
- In this course we will study rational functions and their graphs.
Learner examples
- One half is a rational number.
- Three is a rational number because it is 3 over 1.
- Pi is not a rational number.
- Can you give an example of a rational number?
- We must say if the number is rational or irrational.
adjective
technical
C1
property
5
economically or strategically optimizing
In economics and similar subjects, about a person or group that always chooses the best option for its goals, using all the information it has.
Usage pattern:
a rational [agent/actor/consumer/decision]
Common mistake:
Learners may think "rational" here simply means "smart" or "calm." In economics and decision theory, it has a stricter meaning: following consistent preferences and choosing the option that best reaches a goal. They may also mix this technical sense with the everyday idea of moral goodness; a "rational" choice in this sense is not always a kind or fair one.
Synonyms
utility-maximizing (Technical; emphasizes choosing the option that gives the highest measured benefit (utility).)
|
goal-oriented (More general; focuses on acting to reach goals, not necessarily in a fully mathematical way.)
Antonyms
irrational (In these fields, behavior that does not follow consistent preferences or does not best satisfy the agent’s stated goals.)
|
random (Describes behavior that does not follow a consistent pattern of choosing better options.)
Collocations
rational agent
|rational actor
|rational behavior
|rational choice
|rational expectations
|rational decision-making
Themes
economics
|philosophy
|science
|business
Examples
- Classical economic models assume that each consumer is a rational agent.
- Game theory studies how rational players behave in strategic situations.
- Under the rational expectations hypothesis, people use all available information when forming predictions.
- The experiment showed that real human choices are not always rational in the strict economic sense.
- Policy makers often forget that citizens are not perfectly rational when they make decisions.
Learner examples
- In this model, the buyer is a rational actor.
- Economists often talk about a rational consumer.
- A rational agent will not pay more than the product is worth to him.
- The theory says people are rational, but real people make mistakes.
- Game theory often starts with the idea of rational players.
Grammar
Dictionary form
rational
IPA
GB/ɹˈæʃənəl/
US/ɹˈæʃənəl/
Syllables & stress
ra - tion - al (3 syllables)
Stress on 1st syllable (ra)
Word forms
Adjective
- Base: rational
Word family
Core family
Related words
rationalize
verb
rationalization
noun
Negative and opposite forms
Advanced or less common
rationalism
noun C1
rationalist
noun
Expressions
rational agent
1/ɹˈæʃənəl ˈeɪd͡ʒənt/
fixed phrase
technical
ideal decision-maker who optimizes goals
In economics and related fields, a person or thing that is treated as always choosing the best option to reach its goals.
Examples
- Many economic models start with the idea of a perfectly rational agent.
- A rational agent should never accept a sure loss in a fair game.
- The study questions whether humans can really be seen as fully rational agents.
rational choice
1/ɹˈæʃənəl t͡ʃˈɔɪs/
fixed phrase
decision made through careful reasoning
A decision that is made after thinking clearly about the different options and their results.
Examples
- Given our budget, moving to a smaller office is the rational choice.
- He tried to make a rational choice instead of just doing what felt good in the moment.
- From a health perspective, quitting smoking is the only rational choice.
rational fear
1/ɹˈæʃənəl fˈɪɹ/
fixed phrase
fear that makes sense given real risk
Fear that is understandable and sensible because there is a real and serious danger.
Examples
- After the earthquake, many people had a rational fear of entering old buildings.
- Her fear of losing her job is rational, given the company’s financial problems.
- Being afraid of deep water when you cannot swim is a rational fear.
rational number
1/ɹˈæʃənəl nˈʌmbɚ/
fixed phrase
technical
number expressible as a ratio of integers
A number that you can write as one whole number over another whole number (except zero), like 1/2, -3, or 0.75.
Examples
- All fractions with integer top and bottom are rational numbers.
- The square root of 4 is a rational number, but the square root of 2 is not.
- The teacher asked the class to give three examples of rational numbers.