spectrum

noun

1. A range; a continuous, infinite, one-dimensional set, possibly bounded by extremes.
2. Specifically, a range of colours representing light (electromagnetic radiation) of contiguous frequencies; hence electromagnetic spectrum, visible spectrum, ultraviolet spectrum, etc.
3. The autism spectrum.
4. A set of frequencies that are used for radio-frequency communication; not necessarily a continuous range.
5. The pattern of absorption or emission of radiation produced by a substance when subjected to energy (radiation, heat, electricity, etc.).
6. The set of eigenvalues of a matrix.
7. 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.
8. An abstract object in mathematics created from a commutative ring R and denoted operatorname Spec(R) or operatorname SpecR and said to be the spectrum of R; useful in the study of such rings for providing a geometric object which encodes many of the properties R, and in modern geometry for generalizing the notion of an algebraic variety to that of an affine scheme. Formally, the set of all prime…
9. Specter, apparition.
10. The image of something seen that persists after the eyes are closed.