index
(computer science) A list of record surrogates arranged in order of some attribute expressible in machine-orderable form. To produce a machine-orderable set of record surrogates, as in indexing a book. To compute a machine location by indirection, as is done by index registers. The portion of a computer instruction which indicates what index register (if any) is to be used to modify the address of an instruction.
(mathematics) Unity of a logarithmic scale, as the C scale of a slide rule. A subscript or superscript used to indicate a specific element of a set or sequence. The number above and to the left of a radical sign, indicating the root to be extracted. For a subgroup of a finite group, the order of the group divided by the order of the subgroup. For a continuous complex-valued function defined on a closed plane curve, the change in the amplitude of the function when traversing the curve in a counterclockwise direction, divided by 2π. For a quadratic or Hermitian form, the number of terms with positive coefficients when the form is reduced by a linear transformation to a sum of squares or a sum of squares of absolute values. For a symmetric or Hermitian matrix, the number of positive entries when the matrix is transformed to diagonal form. winding number
(physics) A numerical quantity, usually dimensionless, denoting the magnitude of some physical effect, such as the refractive index.
