Writers Talk About Writing
Popularity Contest: Words for the People
The article was discussing a survey on the popular view of marketers and politicians. "Both have a higher perception of their overall effectiveness than the general populace does," the article said, and "both are disliked by the majority of said populace." One question in the survey asked which professions "clearly do provide value to society," and reported that teachers, scientists, engineers and programmers "received glowing reviews from the general populous."
Two out of three uses are correct. That's a popular mistake, to confuse populace and populous. Throw in the similar-sounding populist, and even more mistakes are made. They mean almost the same thing, only different.
Populace is a noun meaning, literally, "the people." It's often used in place of "the people" in the sense of "population," the people living in a particular place.
But Garner's Modern American Usage notes the connotative differences between populace and population: "population is a neutral term, while populace suggests the rabble or common folk — with a rather superior tone." In fact, most dictionaries say populace is more "the masses," as in the great unwashed, than it is "everyone."
Populous, on the other hand, is an adjective for "having a lot of people," and needs a noun. It's not the same as popular, which usually means it has a lot of people as fans. A city can be both "populous" by having a lot of people, and "popular," which means it's well liked. (Popular also has other meanings — as in these from Merriam-Webster's Unabridged Dictionary: "of or relating to the general public," as in "popular government"; "easy to comprehend," as in a "popular genre of books"; or "marked by attempts to gain general goodwill or to curry favor at large," as in "the hypocritical popular first acts of the usurper" — but we're sticking mostly with popular usage.)
A populist, on the third hand, Webster's New World College Dictionary says, is "any person, esp. a politician or political leader, who claims to represent the interests, views, or tastes of the common people, particularly as distinct from those of the rich or powerful: often applied to someone with demagogic tendencies." Populist often appears with words like authoritarian, so to use it to mean "popular" can backfire, or confuse. An editorial before the election, for example, said that a local politician was likely to have an easier time getting elected, because she was "emphasizing populist positions like opposition to bank bailouts, questioning oil industry profits and help that some residents get from the Affordable Care Act." Whether that's a good position or bad position may depend entirely on whether she's in a red state or blue one.
Populous and populist get confused less often. When they do, though, as Garner's says, the results can be "startling": "California is a state known for its sometimes wacky populace movements that wreak havoc on the state's finances and its residents' civil liberties," for example, probably meant "populist."
All of these confused terms have become common enough to have been noticed by Garner's. They are all at Stage 1 on the five-stage Language-Change Index, meaning they're wrong, but on the radar. They would not be popularly hailed even if they were to move to Stage 2.