Harmonic? Anharmonic? Inharmonic?

In molecular spectroscopy, an anharmonic oscillator has a nonparabolic potential which results in a nonharmonic absorption spectrum, but the same oscillator treated classically has a precisely harmonic vibrational spectrum. To avoid confusion, it is suggested that such an oscillator should simply be called nonlinear. The term “inharmonic” is suggested as an appropriate descriptor for classical oscillators, such as metal bars, that have nonharmonic vibrational spectra even in the linear limit of small vibrations.