Normal - Definition and Overview

The term normal has many meanings, as listed below.

Behavior

In behavior, normal means not deviating very much from the average; "not normal" is often used in a negative sense (improper, sick, etc.). Abnormality varies greatly in how pleasant or unpleasant this is for other people; somebody may half-jokingly be called "pleasantly disturbed". Examples of "normality" are mainstream, temperance, vanilla sex, equilibrium, stability, reality, peace, health, middle way; contrast these with eccentricity, perversion, paraphilia, intersexual, disease, disability, mental illness, addiction, war, crime, fantasy, dream, hallucination, illusion.

Some terms could fit in both lists, for example boredom: too much "normality" can be boring, but boredom is a kind of suffering, which can be considered "not normal".

Quote: It is dangerous to be right on a subject on which the established authorities are wrong. - Voltaire. (It is dangerous not to be "normal" even if you are right).

Sciences and education

• In education, a normal school is a school in which teachers are trained.

• In chemistry, the normality of an acid or an alkali is one way to measure its concentration.

• In computing, a normal number is one that is within the normal range of a floating-point format.

• In computer graphics, more exactly, in raytracing, a surface normal determines how light is reflected from an object.

Mathematics

• In geometry and physics: a normal is a line perpendicular to a surface, see surface normal. The adjective normal is synonymous with "perpendicular".
• In statistics, a normal variable is a random variable that follows the normal distribution.
• In abstract algebra (in particular, group theory): a normal subgroup is a subgroup that is invariant under conjugation.
• In linear algebra: a normal matrix is a matrix which commutes with its conjugate transpose.
• In functional analysis: a normal operator is a linear operator on a Hilbert space that commutes with its adjoint.
• In abstract algebra: a normal extension is a field extension in which certain polynomials can be completely factored into linear polynomials.
• In topology: a normal space is a topological space in which disjoint closed sets can be separated by disjoint neighborhoods.
• In complex analysis, a normal family is a pre-compact family of holomorphic functions.
• In mathematical analysis: a normal number is a number whose digit sequence is random.
• In set theory: a normal function is a continuous strictly increasing function from ordinals to ordinals.
• In category theory: a normal morphism is a morphism that arises as the kernel or cokernel of some other morphisms.

Places

Normal is the name of several places in the United States:

• Normal, Alabama
• Normal, Illinois

Entertainment

• In the Pokémon video game franchise, Normal-type Pokémon are Pokémon that do not have any outstanding elemental characteristics, such as not being able to breathe fire or not being a ghost.

• Normal is the name of a film released in 2003.