spectrum

Etymology

From Latin spectrum (“appearance, image, apparition”), from speciō (“look at, view”). (see scope)

Pronunciation

• (Canada, UK) IPA^(key): /ˈspektɹəm/
• (US) IPA^(key): /ˈspɛkt(ʃ)ɹəm/
• Rhymes: -ɛktɹəm

Noun

spectrum (plural spectra or spectrums)

1. (obsolete) Specter, apparition. [from early 17th c.]
2. A range; a continuous, infinite, one-dimensional set, possibly bounded by extremes.
   • 2012 November 7, Matt Bai, “Winning a Second Term, Obama Will Confront Familiar Headwinds”, in New York Times‎:

     As Mr. Obama prepared to take the oath, his approval rating touched a remarkable 70 percent in some polling — a reflection of good will across the political spectrum.

3. Specifically, a range of colours representing light (electromagnetic radiation) of contiguous frequencies; hence electromagnetic spectrum, visible spectrum, ultraviolet spectrum, etc. [from later 17th c.]
   • 2010 October 30, Jim Giles, Jammed!, in New Scientist,

     Current 3G technologies can send roughly 1 bit of data - a one or a zero - per second over each 1 Hz of spectrum that the operator owns.

4. (psychology, education) The autism spectrum.
5. (chemistry) The pattern of absorption or emission of radiation produced by a substance when subjected to energy (radiation, heat, electricity, etc.).
6. (mathematics, linear algebra) The set of eigenvalues of a matrix.
7. (mathematics, functional analysis) 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. (abstract algebra, algebraic geometry) 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.

Anagrams

• cepstrum, crumpets

Etymology

From spec(iō) (“look at, behold”) +‎ -trum. Confer with speculum.

Pronunciation

• (Classical) IPA^(key): /ˈspek.trum/, [ˈspɛk.trũ]

Noun

spectrum n (genitive spectrī); second declension

1. appearance, image
2. apparition, specter

References

• spectrum in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• spectrum in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
• spectrum in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition, 1883–1887)
• spectrum in Gaffiot, Félix (1934) Dictionnaire Illustré Latin-Français, Hachette