Definition
Repeating unit
A repeating unit is the shortest block that repeats to make a repeating pattern.
What it means
Cover one complete loop of the pattern. Then check that copying that block again and again makes every item. If a smaller block works, the longer block is not the repeating unit.
Remember it
Find one full loop—and make it the shortest one.
Example
In star, star, circle, star, star, circle, … the repeating unit is star–star–circle. The six-item block is two copies of the unit, so it is not the shortest one.
Watch for
A block that repeats but contains two or more copies of a smaller repeating block is not the repeating unit.
Common mix-up
The repeating unit is not always two items long; it may contain one, three, four, or more items.
Exact meaning
A repeating unit is the shortest non-empty finite ordered block whose repeated copies generate a repeating pattern.