The word is also a common adjective for things that are ghostly or immaterial. Spectral Content - an overview | ScienceDirect Topics
The ability of a sensor (like a camera) to distinguish between different wavelengths of light, such as infrared or ultraviolet, beyond what the human eye can see. Spectral
In medicine, spectral features are used to analyze brain waves (EEG) for tasks like sleep staging. 2. Film and Fiction (The Ghostly) The word is also a common adjective for