There are many English words that you can add an “s” to make it plural. But far fewer words become singular when you add an “s”. What are two examples of these much rarer words?
A man owed his friend $63 and repaid him the exact amount in cash without using coins or $1 bills (no online transfers, checks, credit cards or any other tricks) and without requiring change. How did he do it?
Fish. The gh is pronounced as in tough, the o as in women and the ti as in nation. Ghoti is a constructed word to illustrate irregularities in English spelling.
The riddle refers to a variety of meanings of the word fine.
Feeling normal refers to when you feel fine. Extremely thin refers to a fine thread. A punishment refers to being charged a fee. The one who wins refers to an athlete who is physically trained and hardened close to the limit of efficiency. Free from impurity refers to measuring the fineness of precious metals. A keen edge refers to a knife with a fine edge. Refined refers to fine manners or elegance.
A lie. Lies are told, can make people crazy with rage, and most people don’t like to have lies told to them. Lies can’t be harmful though. :) (See what I did there?)