Q: Are the words “plethora” and “dearth” like “sanction” and “invaluable” – i.e., does each have two meanings that are contradictory? I hear “dearth” being used as meaning many, and “plethora” as meaning few. I always thought “dearth” meant few and “plethora” too many.
A: The kind of two-faced word you refer to is sometimes called a “contronym” or a “Janus word,” after the god with two faces. “Cleave,” “sanction,” and “oversight” are examples of contronyms, since they have opposing meanings.
If you’re interested in reading more about these words, I’ve discussed contronyms before on the blog, in a posting last year and in another two years ago.
“Invaluable,” by the way, isn’t one of these words. It has only one meaning: priceless, or beyond value. It never means without value. The negative prefix “in” here suggests something that’s so valuable it can’t be valued.
“Plethora” and “dearth” aren’t contronyms, either. They too have only one meaning each.
We got “plethora” from post-classical Latin, and it has meant the same thing ever since entering English in the 1500s: an overabundance, a plenitude, a large amount.
“Dearth,” first recorded in the 1200s, is from Germanic sources and means a scarcity, an inadequate supply. (It’s related to “dear” in the sense of costly, which once was one of its meanings.)