"Shorts" is a plural noun. Some nouns, like shorts, are grammatically plural and only have a plural form.
"Shorts" is a plural noun or plurale tantum (Latin for "plural only"). Some English nouns, like "shorts", are grammatically plural and only have a plural form.
I can't find my shorts.
I can't find my short.
Remember, "short" (without "s") is an adjective, not a noun.
Have you ever been told that your shorts are too short?
Plural nouns, like shorts, require a plural verb, so we say "shorts have/are" (not "shorts has/is").
Your shorts are too loose.
Your shorts is too loose.
Don't say "a shorts" or "two shorts"; however, you can say "a pair of shorts", "two pairs of shorts", "three pairs of shorts", etc.
There are two pairs of dirty shorts on the bed.
A partial list of articles of clothing that are also plural nouns: