There are certain grammar “rules” that everyone knows, but a lot of them are just wrong, or have so many exceptions that it’s pointless to follow them. Here’s a quick rundown.
An easy error with “an” and “a”
What we get taught: If a word starts with a consonant, the singular article before it is “a.” If it starts with a vowel, then you use “an.”
Why it’s wrong: Using a or an doesn’t depend on whether it’s a vowel or consonant. It depends on the sound. And it may even depend on the dialect. But here’s a simple example: “What are you doing an hour from now?” The word “hour” starts with a consonant, but “a hour” is just wrong because the sound is an open vowel.
As for dialect, an American would probably say “there’s a hospital there,” while a Brit would probably say “there’s an hospital there.” Here’s a vowel example: “There is a universe yet to be discovered.” Why? Because in that case, it starts with a consonant (or semi-vowel) sound: “you-niverse.”
There is never a reason that “their” is singular
What we get taught: The only singular pronouns are he/him/his, she/her/hers, or it/it/its. When the number is singular but the subject is unknown, use the masculine pronouns. They//them/theirs can never be singular, dammit!
Why it’s wrong: Because it’s the goddamn 21st century, and English as a language doesn’t have enough genders to fit the ones that exist. In some ways, it’s kind of nice that English is so genderless, except for those parts when it tries to insist that there are only two genders, and this is one of them. So they/them/theirs are just as valid in the singular as any of the others, and a lot more humanizing than referring to non-binary people as “it.”
It’s really linguistic evolution in action, and very similar to Spanish adopting the conventions of ending nouns and adjectives with either “x” or “@” to be gender-neutral in what’s generally identified as the Latinx or Latin@ movement. (The nice part about @ is that it combines the masculine O ending and the feminine A, although that’s not a hard and fast rule in Spanish, either. La mano and el planeta could tell you a thing or two about that.)
But… here’s the point. Not everyone fits into either he or she and that is a reality of the present. Therefore, it is entirely all right to use they as a third person singular, and it’s best that we refer to it as the gender-neutral form rather than what they call it in German, Romanian, or other languages with the unfortunately dubbed “neuter” case. Because that one always sounds less than, but the idea with ignoring this rule is to be ever more inclusive. “Their” is one (of many) inclusive gender-neutral or non-binary pronouns available now. Ask people theirs, then use them. It’s not that hard.
James’s rule: Don’t add an “S” after the apostrophe to words ending in “S”
What we get taught: If a word ends in “S,” then you make the possessive by only adding an apostrophe, and not an apostrophe S.
Why it’s wrong: This completely ignores how the word is pronounced, and it boils down to this. If you were saying it out loud, would you pronounce the extra S? In most cases, the answer is yes. For example, look at “The car of Jon” vs. “Jon’s car.” Extra S gets pronounced. So… “The car of James” vs. “James…” That’s right, when spoken, it sounds like “Jameses car,” so the correct possessive is “James’s car.” When you get into plural possessives ending in S, as the link points out, it’s the same deal. When a family named Jones owns a thing, then you pluralize first, then follow the rule for plural possessives and wind up with “The Joneses’ House.”
To glibly split infinitives is wrong
What we get taught: It is wrong to split an infinitive in English, by which we mean nothing can come between “to” and the basic verb form. To be, to do, to go, to eat, etc.
Why it’s wrong: Because some pedant in 19th Century England decided to just make things up. But this rule doesn’t make any sense at all, either. It’s right up there with the stupidity of throwing that extra “U” into words like color or flavor. And, bonus points: English is one of the few languages with infinitives that can even be split because, unlike most other languages that do it with a prefix, suffix, or stem word to create a singular word infinitive, we insist on throwing a preposition in front of a mostly neutral form to create an infinitive. Ooh, look. That was an infinitive right there! English is weird.
Ending a sentence with a preposition is something to watch out for
What we get taught: Never end a sentence with a preposition. It’s wrong. Don’t do it!
Why it’s wrong: Cue up another pedant, in this case John Dryden, who, according to that link, was not well-liked by his contemporaries despite his success, or maybe because of it. His whole shtick was trying to force Latin Grammar onto the English language because he really loved him some Latin. But here’s the problem: Although English is partly a Germanic language and German follows a lot of the grammar left over from Latin, English managed to escape that first via Anglo Saxon and next via a mega-dose of Romance Language grammar via the Norman Invasion. Preposition placement in Latin was very carefully dictated. in English, not so much. Put that preposition wherever you think it needs to go.
There’s a very famous anecdote often attributed to Winston Churchill, but probably not him, in which a subordinate made a note on a speech or some such telling him to not end a sentence with a preposition. The reply, which was probably not Churchill, but rather just a joke, was that he wrote back, “This is an impertinence up with which I will not put.” The point here being that this sentence explains perfectly why this rule is so stupid and useless.
“I” before “E” except after “C” is the best of policies
What we get taught: I before E except after C, or when pronounced “A,” as in “neighbor” or “weigh.”
Why it’s wrong: Because there’s not a single thing right about it? There are more exceptions to this rule than there are rules, so it shouldn’t be taught at all. So where did it come from? Simple. Early grammar textbooks in the mid-19th century, designed to be shipped out to remote schoolhouses, and which included lots of lists of little rhyming rules like this that were sometimes right but often wrong. This one just happened to be short and simple, and so it stuck, even though it’s very, very wrong.
And never start a sentence with a conjunction
What we get taught: Using and, so, but, etc. should never come at the start of a sentence.
Why it’s wrong: But so many writers do it. And it can be very useful. So why the problem? Again, it’s made up. Or, rather, it’s an oversimplification of when conjunctions are needed to connect two clauses directly, or when they’re not. The problem, as is frequently the case, are the fanboys — for, and, nor, but, or, yet, so. These cannot start sentences because they do connect to the previous clause. The other conjunctions? Not so much, so have at them!
As they say, you have to learn the rules before you can break them. But sometimes, you have to learn that the rules are just plain wrong, and these are examples of that. If you have any favorite grammar “rules” that are wrong, share them in the comments.