# spectrum

Pronunciation: say "SPEK-truhm" /ˈspɛktɹəm/

## Noun

1. A continuous range of values or qualities, possibly bounded by extremes at either end.
   - Simple: A full range of related things, stretching from one extreme to its opposite.
   - _Opinions on the issue span the full spectrum, from outright rejection to enthusiastic support._
   - _Personality traits fall along a spectrum rather than into a few neat categories._
2. A range of colors representing light of continuous, neighboring frequencies, as seen when white light is split apart.
   - Simple: The band of colors that light splits into, like the colors in a rainbow.
   - _The prism spread the beam into a bright spectrum across the wall._
   - _Each color in the spectrum corresponds to a different wavelength of light._
3. The full range of autism diagnoses, recognizing that autistic traits vary widely in kind and severity from one person to another.
   - Simple: A way of describing autism that covers a wide range of traits and abilities.
   - _Her son is on the spectrum and thrives with a predictable daily routine._
   - _Clinicians now place many earlier diagnoses under the broader autism spectrum._
4. The pattern of radiation a substance absorbs or emits when it is exposed to energy such as heat, light, or electricity.
   - Simple: The pattern of light a material gives off or takes in when energy reaches it.
   - _Heating the sample produced an emission spectrum unique to that compound._
   - _Astronomers analyze the spectrum of distant stars to identify their elements._
5. An image of something just seen that lingers in vision after the eyes are closed.
   - Simple: A picture you still seem to see after you shut your eyes.
   - _Long after looking away from the sun, a faint spectrum drifted across his closed eyes._
   - _Each time she blinked, a glowing spectrum of the candle hovered in the dark._
6. In linear algebra, the set of all eigenvalues associated with a given matrix.
   - Simple: In math, the set of special values, called eigenvalues, that belong to a matrix.
   - _The spectrum of a symmetric matrix consists entirely of real numbers._
   - _Computing the spectrum requires solving the characteristic equation of the matrix._
7. For a bounded linear operator, the set of scalar values λ for which the operator A − λI has no bounded inverse; a generalization of the eigenvalue sense from linear algebra.
   - Simple: In advanced math, a set of special number values tied to a kind of function called an operator.
   - _The spectrum of a bounded operator is always a closed subset of the complex plane._
   - _Unlike the finite-dimensional case, the spectrum can contain values that are not eigenvalues._
8. An abstract mathematical object built from a commutative ring R, written Spec(R), whose points are the prime ideals of R; it gives a geometric way to study the ring and generalizes algebraic varieties.
   - Simple: In advanced math, a special object built from a number system called a ring that lets people study it using shapes.
   - _The spectrum of a ring forms a topological space whose points are its prime ideals._
   - _Geometers study the spectrum to translate questions about rings into geometric ones._

## Noun

9. A specter or apparition; a ghostly figure that appears to the living. *(obsolete)*
   - Simple: A ghost or spirit that appears to someone.
   - _By candlelight the old man claimed a silent spectrum stood at the foot of his bed._
   - _Travelers feared the spectrum said to haunt the ruined abbey after dusk._

## Origin

From Latin spectrum ("appearance, image, apparition"), which comes from speciō ("to look at, view"). It is a doublet of specter.

Source: DictionaryAI, https://dictionaryai.com/define/spectrum (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).