spectrum

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

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

Education, Human sciences, Psychology, Sciences Usually, With the The autism spectrum.

Communications, Electrical engineering, Engineering, Natural sciences, Physical sciences, Telecommunications A set of frequencies that are used for radio-frequency communication; not necessarily a continuous range.

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

Linear algebra, Mathematics, Sciences The set of eigenvalues of a matrix.

Mathematics, Sciences 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.

Algebraic geometry, Geometry, Mathematics, Sciences 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 ideals R equipped with the Zariski topology and augmented with a sheaf of rings called the structure sheaf, generated by the B-sheaf on the distinguished open sets D_f which assigns the localization of R at f to each set D_f, regarded as a ring of functions on D_f. See Spectrum of a ring on Wikipedia.Wikipedia

Obsolete Specter, apparition.

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