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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?

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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.

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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.

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  • \$\begingroup\$ are wave and waveform same terms? \$\endgroup\$ – user3559780 Jun 5 '16 at 13:45
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    \$\begingroup\$ Sorry. No they are not the same. A wave is a propagating physical property. \$\endgroup\$ – Mario Jun 5 '16 at 15:51
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    \$\begingroup\$ 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) . \$\endgroup\$ – Sredni Vashtar Jun 5 '16 at 17:09

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