Unit (noun)

1. An individual thing or person regarded as single and complete, but often forming part of a larger group, set, or category.
2. A standard measure of quantity, such as a foot or a pound.

Origin:

From old french unite, from latin unitatem (nominative unitas) "oneness, unity, agreement", from unus "one".

Examples:

1. The unit of measurement for length is the meter.
2. The soldiers were organized into units of ten.
3. The cost of the product is given per unit.
4. The apartment building was divided into residential units.
5. The unit of currency in this country is the dollar.