Language changes. English evolves. But even most of us who accept this have our “stickling points”, the (mis)uses we can’t abide. One of mine is “criteria” used as a singular.
“The number one criteria is who can beat Trump,” former Democratic presidential hopeful Howard Dean said last month of the nomination battle then between Joe Biden, Bernie Sanders and Elizabeth Warren. It’s criterion, Howard. One criterion, two criteria. (I know there are bigger things to worry about at the moment. We cover them amply elsewhere. Working from home will leave us sticklers with more time to stickle. So let’s press on.)
Plurals can become singular over time. “There are bad news from Palermo,” Percy Bysshe Shelley once wrote. “Criteria” may become an acceptable singular too one day but, for now, it grates. So do “a strata” and “a phenomena”. Strata and phenomena are plurals; the singulars are “stratum” and “phenomenon”, and, as The Oxford Companion to the English Language says, their misuse is “disliked (often intensely) not only by purists but by many who consider themselves liberal in matters of usage”.