Sad: Showing, expressing, or causing sorrow or gloom; depressing; inadequate.
Sad is neither new nor obscure: it’s been with us since Old English, and even young children understand at least one of its meanings. But it’s been in the foreground in recent months thanks to a series of tweets published by a front-runner in the U.S. presidential primaries. “I believe we may be witnessing an evolution in the use of that word,” said Mike Vuolo, co-host of the language podcast “Lexicon Valley” in a February episode. If so, it would be only the most recent twist in sad’s long and interesting history.