Much has been written about the dangers of using spelling checkers without brain in gear. Spelling checkers won’t tell you when you use “there” when you meant “their,” “then” when you meant “than,” or “window” when you meant “widow,” as we did a few weeks back.

A poem that makes the rounds of copy editors every so often highlights the dangers. It begins:

Eye halve a spelling checker, It came with my pea sea. It plainly marks four my revue Miss steaks eye kin knot sea.

But spelling checkers can also allow you to think that you’re spelling a word correctly when you’re not, or that there are two different “correct” spellings for the same word. There sometimes are, of course: “judgement” and “judgment” are the same word, with the first spelling preferred in British English; or “worshipper” and “worshiper,” the former preferred by Associated Press style and the latter by New York Times style.

This confused Chikodi Chima, an editor at breakingmedia.com, who wrote:

“Since most of my writing is done online, I rely on spellcheckers within whatever word processor I use to catch mistakes. When I write therefor, I’m told it is correct to spell it the aforementioned way, or as therefore. Is there one correct spelling, or are there different circumstances for each usage?”

On the Internet, a rash of people say that “therefor” is merely an archaic spelling of “therefore.” But they’re actually two different words. “Therefore,” the one seen most frequently, is pronounced with the emphasis on the first syllable. It’s an adverb and a conjunction, often connecting two parts of a sentence, as in “I think, therefore I am.” It means “consequently,” or “for that reason.” “Therefor,” pronounced with the emphasis on the second syllable, is also an adverb, but almost never a conjunction. It’s used mainly in legal or accounting contexts to mean “in return for that,” as in a law defining a gift as “anything of value unless consideration of equal or greater value has been given therefor.”

In his Garner’s Modern American Usage, Bryan A. Garner, also the editor of Black’s Law Dictionary, says that lawyers often misuse “therefor” when they mean “therefore,” and calls it jargon. “If the good writers,” he says, “start overusing it, they’ll risk no longer being called ‘good.’”

The same thing happens with “discrete,” which is seen by some as a variant spelling of “discreet.” As we’ve mentioned, it’s not: “Discreet” means “cautious” or “careful”; “discrete” is “separate” or “distinct.” (You can have “discreet” and “discrete” affairs, for example.)

Because “discrete” is less common but will pass spelling checkers, it shows up more often than it should when “discreet” is meant, and has reached Stage 1 on Garner’s Language-Change Index, meaning some people do it, but it’s really, seriously wrong.

But also possibly because “discrete” is less familiar, it shows up less often than it should in its proper place: The misuse of “discreet” when “discrete” is meant has reached Stage 2 of the Language-Change Index, meaning it’s used a lot but still considered wrong.

In one Garner analogy, Stage 1 is a mortal sin, while Stage 2 is merely a capital sin.

Therefore, be discreet when you use your spelling checker, and look for words that should be discrete, or risk being punished therefor.

Merrill Perlman managed copy desks across the newsroom at The New York Times, where she worked for 25 years.