Noun Plurals
Most nouns change their form to indicate number by adding "-s" or "-es", as illustrated in the following pairs of sentences:
When Matthew was small he rarely told the truth if he thought he was going to be punished.
Many people do not believe that truths are self-evident.
As they walked through the silent house, they were startled by an unexpected echo.
I like to shout into the quarry and listen to the echoes that return.
He tripped over a box left carelessly in the hallway.
Since we are moving, we will need many boxes.
There are other nouns which form the plural by changing the last letter before adding "s". Some words ending in "f" form the plural by deleting "f" and adding "ves," and words ending in "y" form the plural by deleting the "y" and adding "ies," as in the following pairs of sentences:
The harbour at Marble Mountain has one wharf.
There are several wharves in Halifax Harbour.
Warsaw is their favourite city because it reminds them of their courtship.
The vacation my grandparents won includes trips to twelve European cities.
The children circled around the headmaster and shouted, "Are you a mouse or a man?"
The audience was shocked when all five men admitted that they were afraid of mice.
Other nouns form the plural irregularly. If English is your first language, you probably know most of these already: when in doubt, consult a good dictionary.