Section 4.1 Units vs Dimensions

It is easy to get units and dimensions mixed up. It helps to think of dimensions as fundamental and usually unspoken whereas units are derived from the dimension and quantify the dimension.

As an example, let’s say you are recruiting someone to play on your basketball team. You know that in basketball, there are significant advantages for tall players. You might ask a potential Canadian player “How tall are you?” and she might reply “I am 1.8 meters tall”. In this case, the dimension we are considering is length (aka “height” in colloquial terms), and the unit we are using to describe the dimension length is meters. However, if you ask an American player who is the exact same height as the Canadian player, she might reply “I am 5 feet 11 inches tall”. In this case, the dimension is still length, but now the units being used to describe that dimension, are now feet and inches.