word-forming element meaning "of or by a spectroscope," also "of radiant energy," from combining form of spectrum.
Entries linking to spectro-
spectrum n.
1610s, "apparition, specter," from Latin spectrum (plural spectra) "an appearance, image, apparition, specter," from specere "to look at, view" (from PIE root *spek- "to observe"). Meaning "visible band showing the successive colors, formed from a beam of light passed through a prism" first recorded 1670s. Figurative sense of "entire range (of something)" is from 1936.
spectrogram n.
"photograph of a spectrum," 1890, from spectro- + -gram.