spectrum

noun

1. 1

   A range; a continuous, infinite, one-dimensional set, possibly bounded by extremes.

2. 2

   Specifically, a range of colours representing light (electromagnetic radiation) of contiguous frequencies; hence electromagnetic spectrum, visible spectrum, ultraviolet spectrum, etc.

3. 3

   The autism spectrum.

4. 4

   The pattern of absorption or emission of radiation produced by a substance when subjected to energy (radiation, heat, electricity, etc.).

5. 5

   The set of eigenvalues of a matrix.

6. 6

   Of a bounded linear operator A, the set of scalar values λ such that the operator A—λI, where I denotes the identity operator, does not have a bounded inverse; intended as a generalisation of the linear algebra sense.

7. 7

   (abstract algebra) The set, denoted Spec(R), of all prime ideals of a given ring R, commonly augmented with a Zariski topology and considered as a topological space.

8. 8

   Specter, apparition.

9. 9

   The image of something seen that persists after the eyes are closed.