Singular = 1
Plural = more than one
Plural nouns in English follow a few consistent patterns.
Use –es for words ending in s, x, z, ch, sh
* Adding -es is more common. But adding –s is considered acceptable too.
Some nouns have the same form whether singular or plural. No need to add -s or -es, even when you're talking about many.
So whether you're talking about one jet or an entire fleet, you just say aircraft. No "s", no "es".
Other nouns like this include:
“I caught one fish.”
“We saw ten fish in the pond.”
“The aquarium contains fishes from the Amazon, the Pacific, and the Atlantic.”
A plural-only noun refers to a noun that exists only in its plural form.
They all refer to things that are essentially one item, but made of two parts—so the plural form is the default.
These nouns don’t have a singular version, even when referring to just one item or concept.