The fundamental is harmonic #1. This is the case for essentially all additive synthesizers for example. Overtones are any partials other than the fundamental.

The fundamental is harmonic #1. This is the case for essentially all additive synthesizers for example. Overtones are any partials other than the fundamental. While overtones CAN be non-harmonic (notably in bells), I think it's fair to say that most of them, or at least the most important ones, are usually harmonics. This is because the terms "fundamental" and "overtone" are historically music terms, and are generally applied to sounds we perceive as tonal or musical: and such sounds are largely composed of harmonics.