Units of Measurement are used to talk about quantity. Common units include:
- length: meter, mile, kilometer…
- weight: pound, stone, kilogram…
- liquid: liter, gallon…
Singular & Plural
Units of measurement usually have a singular and plural form:
I’ve lived here 1 year.
That wall is 3 meters tall.
This tank will hold just 2 liters.
However, if we use the unit of measurement in a compound then we keep it singular. Compare these two:
He is 6 years old.
He is a 6 year old child.
In the first example, years modifies old and is plural. In the second example year is part of a compound year old which modifies child.
There are, however, exceptions and in some cases we can use both the singular and the plural. For example, both of these are correct:
The tree is 10 feet tall.
The tree is 10 foot tall.