# What is the difference between the terms wave, waveform, and signal?

What is the difference between wave, waveform, and signal? Or do they have the same meaning? Can they be used in place of one another?

• – Whiskeyjack Jun 5 '16 at 12:30
• @Whiskeyjack yeah, but the OP should read it with a grain of salt. "A wave needs a medium" and "for example, light waves" in the same answer... – Sredni Vashtar Jun 5 '16 at 16:37

## 2 Answers

A signal is simply something observable changing across one or multiple dimensions. As that, it carries some changing state, which means it has some information¹.

For example, air pressure changing over time might be an audio signal, brightness changing over length might be a barcode (signal), and voltage changing over time is what we typically call an electric signal.

Now, a wave is usually a physical entity that actually fulfills a periodic, harmonic motion. As that, it is a special kind of signal.

Waveform is a term from the radio (and possibly audio) engineering. In that, you modify a (usually harmonic), periodic signal (i.e. a wave) with varying parameters (i.e. another signal) to give it the form you want. Radio modulations are a typical example of that – FM broadcasting is a classical waveform to modify radio waves according to another signal (in that case, audio that you want to broadcast).

I'd strongly recommend using waveform only in a context where the usage of "I know there's information in this wave's modification over time" is important, wave only when you have a (typically propagating) periodic signal, and signal whenever you describe something changing in general.

People that do a lot of signal processing might actually imply periodic nature if they read wave. Things like "square wave" already feel a bit off, because they're not harmonic (within finite bandwidth).

¹I'll not go into the information theory aspects of that, because it will quickly expand far beyond the scope of this question, and will lead to me explaining a lot of stochastics.

By definition a signal is something that carries information. A waveform is a representation of physical quantity such as voltage or a current over time. If this physical quantity carries information then it is a signal.

In practice, however, the terms signal and waveform are often used synonymously.

• are wave and waveform same terms? – user3559780 Jun 5 '16 at 13:45
• Sorry. No they are not the same. A wave is a propagating physical property. – Mario Jun 5 '16 at 15:51
• I guess the problem arises from the fact that in electronics people use (rather loosely) the term "wave" as a shorthand for "waveform". Neither of those, by the way, need to be periodic, nor harmonic (oscilloscope triggering in the pre-digital era is probably the cause for this misunderstanding) . – Sredni Vashtar Jun 5 '16 at 17:09