Are these words two-faced?
There are four people at a dinner party. By midnight, two people had left. How many people are left at the party?
Left is just one of many words or expressions known as a contronym—or contranym—a word that has two meanings that are opposite or nearly opposite. In this example, left means both “leave” (two people had left) and “remain” (How many people are left?), which are antonyms. An antonym is a word that is opposite in meaning to another.
Contronyms are also known as Janus words. Janus was an ancient Roman god with two faces that looked in opposite directions, so you can see how he came to be associated with contronyms. (You might be surprised to know that Janus is also connected to the month of January.)
Another term for these words is auto-antonym, or a word that means the opposite of itself. Technical terms for this phenomenon are enantiosemy, enantionymy, or antilogy.
You’re likely familiar with many of these contronyms, even if you don’t realize it. So check out some of the most common ones, before you check out.