Spectral comes from specter/spectrum + -al; from Latin spectrum ('apparition, appearance'), from specere ('to look at'). The historical chain includes Latin spectrum and Latin specere. Older glosses in the chain include "apparition, appearance" and "to look at", which help explain the semantic range of the modern word. Morphologically, spectral is best read as compound, suffixal formation, and borrowing, yielding an English adjective shaped by both form history and later usage. In current English it functions as an adjective, with the sense "ghostly in appearance, or relating to a spectrum of light". English derivatives include spectrally; related forms include specter and spectrum. The result is an English adjective whose etymology preserves the older forms while supporting the word's specialized modern meaning.