I wrote the word "trousers" in another thread, and realized that there does not exist a singular as a noun. (There does as an adjective - "trouser pockets") After some thinking, it appears that these nouns that exist only in the plural fall into three categories:
- Items of clothing: trousers, pants, jeans, leggings, bloomers, and of course clothes.
- Tools: pliers, scissors, forceps, glasses and binoculars.
- Wealth: wages, riches, earnings, belongings.