Contronyms

Contronyms are words that are their own antonyms.  "Contronyms" is a new word for me, though I've encountered the problem before and wondered why we even had words like this.  I have also avoided using words like "sanction," not wanting to deliberately introduce confusion into what I was saying or writing:

Sanction can mean "give official permission or approval for (an action)" or conversely, "impose a penalty on."

And then there's the word "left."

She left, so who's left?

The first use means someone has gone away and is no longer there, but the second use asks who is still there.

Fix can mean to repair something that's broken, or it can mean to castrate.  This cat knows only the first meaning, apparently.

Words can be slippery sometimes.  To see more opposites in the same word, read 25 Words That Are Their Own Opposites and 75 Contronyms (Words with Contradictory Meanings).