Rhythm – Are beats that are repeated a particular number of times within a tempo/beat/pulse; a pattern of sounds of different lengths

Note:

1. Rhythm does not involve pitch as melody does.

2. Melody involves pitch and rhythm

The best way to remember what rhythm means is to use the mnemonic:

What is rhythm

Repeat this three times at a set beat and this becomes a rhythm (don't change the pitch).

Even better would be:

A pattern of sounds of different lengths

Repeat this three times at a set beat and this too is a rhythm (again don't change the pitch).