6. Signals

A signal is a number linked to something. When a number is analyzed without context, it is part of maths. When it relates to anything else, it is a signal.

Usually signals link a measurement to a sample. These measurements may provide more than one number, so a signal may contain more than one value per sample, and usually a single measurement doesn't provide context or utility, so we make multiple measurements. We need to organize these measurements by a parameter we call the Index.

In many applications the index is time, or location, or a combination of time and location, and a measurement records an event for further analysis. But the index can be anything that allows differentiation of the measurements.

Mathematics and signals share a common essence. In nature and behavior. Signals tend to apply mathematics into the world.