Spectrum
Etymology
From Latin spectrum, “appearance, apparition,” from specere, “to look at”; it once meant a spectre or mental image. Isaac Newton repurposed it for the band of colors a prism throws from white light, and from that ordered range came the general sense of any graded continuum.
noun · /SPEK-trum/
A continuous range between two extremes along which things vary by degree.
What it names
The “not either/or” territory — a way of placing something on a graded scale instead of forcing it into one of two boxes.
Example
Political views rarely split in two; they sit along a spectrum with countless positions between the poles.
Related idea
A spectrum usually runs between two named poles; a continuum stresses only that there are no sharp breaks anywhere along it.
noun · /SPEK-trum/
The band of colors produced when light is split, or the full range of electromagnetic waves.
What it names
the rainbow from a prism; radio-to-gamma electromagnetic waves
Example
A prism spreads white light into its spectrum.
Related idea
The figurative “range between two extremes” is borrowed straight from this optical band.