gamo

A word that grew upwards from its lowest note. Guido of Arezzo needed a name for the note below the bottom of the existing scale, so he took the next Greek letter, gamma, and stuck the singing syllable ut on it. Gamma ut became gamut, and then, the way these things go, the name of one note became the name of everything above it. When somebody says a performance ran the whole gamut, they are unknowingly naming a single medieval bass note.

Two senses, both alive. The technical one is a musical scale, the run of notes you practise: maĵora gamo, minora gamo, ludi gamojn. The extended one is a range or a spread of anything at all - a range of colours, of prices, of feelings - and Esperanto uses it as freely as French uses gamme. English lost the musical sense of gamut almost entirely and kept only the figurative one, so English speakers tend to under-use this word by half.

Not the Greek letter, and not the radiation. The letter itself is gamo in some older texts but gama in modern use, and gama-radioj are gamma rays. Nor is this the -gramo of telegramo, which is a different Greek root altogether. When you want the musical scale and want to be unmistakable, skalo also exists as a borrowing, but gamo is the word a musician will use.