1. A list of record surrogates arranged in order of some attribute expressible in machine-orderable form.

2. To produce a machine-orderable set of record surrogates, as in indexing a book.

3. To compute a machine location by indirection, as is done by index registers.

4. The portion of a computer instruction which indicates what index register (if any) is to be used to modify the address of an instruction.

1. Unity of a logarithmic scale, as the C scale of a slide rule.

2. A subscript or superscript used to indicate a specific element of a set or sequence.

3. The number above and to the left of a radical sign, indicating the root to be extracted.

4. For a subgroup of a finite group, the order of the group divided by the order of the subgroup.

5. 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.

A numerical quantity, usually dimensionless, denoting the magnitude of some physical effect, such as the refractive index.