Repetition, Pattern, and Rhythm relate to each other.

Pattern---Pattern is a combination of elements or shapes repeated in a recurring and regular arrangement.In pattern, elements are repeated in the same way throughout the whole composition, as in the example above. In the example of rhythm below, the same elements are used, but with variations. See if you can sense and understand the difference.

Pattern as decoration

We are all familiar with the use of pattern as decoration, from clothing, to everyday objects, to home decorating . Below is an example of an elaborate use of pattern in home decoration.

Repetition --Repetition refers to one object or shape repeated; Repetition is an object, form, or figure that is repeated.

Symbolic uses of pattern---Pattern is often used symbolically to represent many things: people, beliefs, the natural world, history, tradition.  

Colors and shapes have specific meanings, and are passed down from generation to generation. 
The predictability of pattern is important in establishing a historical tradition and cultural practice.

Rhythm--is a combination of elements repeated, but with variations. Rhythm is like pattern, in that the same elements (i.e.shape, line) are repeated; however, with rhythm there are slight variations in the pattern. 

Rhythm is easily perceived but complex and subtle. Think of  water on a beach; it  continually breaks on the shore in lines that are repeated,  yet each one is different.  Rhythm is most easily understood within music. Rhythm represents our desire for order. Rhythm is like our own heartbest; it gives us a sense of the pulsing of life.

 Source: https://www.sophia.org/tutorials/design-in-art-repetition-pattern-and-rhythm