Here’s an ambiguous sentence for you: “Because of the agency’s oversight, the corporation’s behavior was sanctioned.” Does that mean, “Because the agency oversaw the company’s behavior, they imposed a penalty for some transgression,” or does it mean, “Because the agency was inattentive, they overlooked the misbehavior and gave it their approval by default”? We’ve stumbled into the looking-glass world of contronyms—words that are their own antonyms.
1. Sanction (via French, from Latin sanctio(n-), from sancire ‘ratify,’) can mean “give official permission or approval for (an action)” or conversely, “impose a penalty on.”
2. Oversight is the noun form of two verbs with contrary meanings, “oversee” and “overlook.” Oversee, from Old English ofersēon (“look at from above”) means “supervise” (medieval Latin for the same thing: super-, “over” plus videre, “to see.”) Overlook usually means the opposite: “to fail to see or observe; to pass over without noticing; to disregard, ignore.”
3. Left can mean either remaining or departed. If the gentlemen have withdrawn to the drawing room for after-dinner cigars, who’s left? (The gentlemen have left and the ladies are left.)
4. Dust, along with the next two words, is a noun turned into a verb meaning either to add or to remove the thing in question. Only the context will tell you which it is. When you dust are you applying dust or removing it? It depends whether you’re dusting the crops or the furniture.