Two feet measuring less than two feet.

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.