Definition
Non-standard unit
A non-standard unit is an informal repeated unit used to measure something.
What it means
You can measure a desk with identical cubes, paper clips, or hand spans instead of centimetres. The result tells how many chosen units fit. Different-sized units can give different numbers for the same object, so you must name the unit you used.
Remember it
Same-sized units, end to end: no gaps, no overlaps, and always name the unit.
Example
Nine identical cubes fit from one end of a book to the other with no gaps or overlaps. The book is 9 cubes long.
Watch for
Centimetres on a ruler are standard units because their size is agreed. Cubes used just for one classroom measurement are non-standard units.
Common mix-up
Non-standard does not mean careless. The units still need to be equal in size and placed consistently.
Exact meaning
A non-standard unit is a chosen unit that is not fixed by an agreed measurement system. For a fair measurement, equal-sized copies are repeated with no gaps or overlaps.