(1) common are

clothes

equipment

Luggage/luggage

jewellery

traffic

information

machine

goods

produce

scenery

They refer to many similar things, and their usage is equivalent to uncountable nouns:

The form is always singular, and there is no plural form. When the subject is used, the predicate is singular.

For example:

The old machine is out of date.

These old machines are out of date.

② Not directly used with a(n) or numbers. Use more, less, some, a piece, an article, etc.

For example:

There are five pieces of furniture in each room.

There are five pieces of furniture in each room.

③ If pronouns are needed, use singular pronouns.

For example:

Do you want to see my jewelry? It's in the box.

Do you want to see my jewelry? It is in my box.