IRRATIONAL

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 Dictionary entry overview: What does irrational mean? 

• IRRATIONAL (noun)
  The noun IRRATIONAL has 1 sense:

1. a real number that cannot be expressed as a rational number

  Familiarity information: IRRATIONAL used as a noun is very rare.

• IRRATIONAL (adjective)
  The adjective IRRATIONAL has 2 senses:

1. not consistent with or using reason

2. real but not expressible as the quotient of two integers

  Familiarity information: IRRATIONAL used as an adjective is rare.

 Dictionary entry details 

• IRRATIONAL (noun)

Sense 1

Meaning:

A real number that cannot be expressed as a rational number

Classified under:

Nouns denoting quantities and units of measure

Synonyms:

irrational; irrational number

Hypernyms ("irrational" is a kind of...):

real; real number (any rational or irrational number)

Hyponyms (each of the following is a kind of "irrational"):

transcendental number (an irrational number that is not algebraic)

algebraic number (root of an algebraic equation with rational coefficients)

• IRRATIONAL (adjective)

Sense 1

Meaning:

Not consistent with or using reason

Context example:

irrational animals

Similar:

blind; unreasoning (not based on reason or evidence)

reasonless (not endowed with the capacity to reason)

nonrational (not based on reason)

superstitious (showing ignorance of the laws of nature and faith in magic or chance)

Also:

incoherent (without logical or meaningful connection)

illogical; unlogical (lacking in correct logical relation)

unreasonable (not reasonable; not showing good judgment)

Antonym:

rational (consistent with or based on or using reason)

Derivation:

irrationality (the state of being irrational; lacking powers of understanding)

Sense 2

Meaning:

Real but not expressible as the quotient of two integers

Classified under:

Relational adjectives (pertainyms)

Context example:

irrational numbers

Domain category:

math; mathematics; maths (a science (or group of related sciences) dealing with the logic of quantity and shape and arrangement)

Antonym:

rational (capable of being expressed as a quotient of integers)

Pertainym:

ratio (the relative magnitudes of two quantities (usually expressed as a quotient))

 Context examples 

An anxiety disorder characterized by an intense, irrational fear of an object, activity, or situation.

(Phobia, NCI Thesaurus)

"No," said he, "I never said any thing so irrational. Don't palm all your abuses of languages upon me."

(Sense and Sensibility, by Jane Austen)

An anxiety disorder characterized by an intense, irrational fear of venturing out into open places or situations in which help (or escape) might not be available should excessive anxiety or panic symptoms develop.

(Agoraphobia, NCI Thesaurus)

An irrational fear of being in a confined space.

(Claustrophobia, NCI Thesaurus)

Sudden extreme anxiety or fear that may cause irrational thoughts or actions.

(Panic, NCI Dictionary)

An extreme, irrational, fear of something that may cause a person to panic.

(Phobia, NCI Dictionary)

It is a strong, irrational fear of something that poses little or no real danger.

(Phobias, NIH: National Institute of Mental Health)

Anxiety disorders in which the essential feature is persistent and irrational fear of a specific object, activity, or situation that the individual feels compelled to avoid.

(Phobia, NLM, Medical Subject Headings)

A disorder characterized by the presence of persistent and recurrent irrational thoughts (obsessions), resulting in marked anxiety and repetitive excessive behaviors (compulsions) as a way to try to decrease that anxiety.

(Obsessive Compulsive Disorder, NCI Thesaurus)

A mental disorder caused by intrinsic disease which is characterized by persistent or recurrent irrational beliefs.

(Organic Delusional Syndrome, NCI Thesaurus)