# Normal

In mathematics, normal can have several meanings:

• Surface normal, a line that is perpendicular to a surface
• Normal distribution, a type of probability distribution in probability theory and statistics
• Normal extension, in abstract algebra, a certain type of algebraic field extensions
• Normal family, a pre-compact family of holomorphic functions
• Normal function, a continuous strictly increasing function from ordinals to ordinals
• Normal matrix, a matrix which commutes with its conjugate transpose
• Normal mode, a special type of solution in an oscillating system
• Normal morphism, is a morphism that arises as the kernel or cokernel of some other morphisms
• Normal number (computing), a number that is within the normal range of a floating-point format
• Normal number, a number whose digit sequence is random
• Normal operator, a linear operator on a Hilbert space that commutes with its adjoint
• Normal space, a topological space in which disjoint closed sets can be separated by disjoint neighborhoods
• Normal subgroup, a subgroup that is invariant under conjugation in abstract algebra

Some closely related terms are

• Normalizing constant, a constant which scales a mathematical object so that its "size" is equal to one
• Unit vector, a vector which has been scaled in such a manner
• Orthonormality: two vectors are said to be orthonormal if they are both orthogonal to each other and unit vectors.