Important Rule: A proper noun always begins with a capital letter.
Note:
When these words are used with numbers (e.g., two dozen, three hundred), the form stays the same.
But when used alone, we form plurals by adding -s:
e.g. dozens, hundreds, thousands.
We paid customs at the airport.
He has good manners.
Smoking is not allowed on the premises.
The soldiers stayed in the army quarters.
I lost my spectacles again!
The prisoner was bound in irons.
He joined the armed forces.
We bought two tins of soup.
They went walking in the woods.
John gave Mary a book.