Only in plural...

 Did you know that some English words exist only in plural form?

They cannot be used with numbers. They include the names of certain tools, instruments and articles of clothing which have two parts.

Here we have some examples...

Tools and instruments: binoculars, headphones, sunglasses, glasses, scissors, tweezers.

Clothing: jeans, pyjamas, tights, knickers, shorts, trousers, pants.