Nouns which are always plural

Certain nouns only have plural forms:

These scissors are for cutting paper.
Your clothes are dirty.
Have you seen my glasses? I want to read the newspaper.
The table of contents should not contain any pictures.
I live on the outskirts of the city.

Some of these nouns are often used with the expression a pair of, as they refer to things made up of two parts:

a pair of trousers
a pair of jeans
a pair of shoes
a pair of slippers
a pair of glasses
a pair of gloves
a pair of earrings

The nouns people (meaning more than one person) and police are always plural:

People say that the police are investigating the case.

People can refer to a nation, religion or race, in which case it is considered as a singular noun and can be used in a singular or plural form:

They are a welcoming and hospitable people.
At college, he took a course on the history of the peoples of the British Isles.