Starting a sentence with a conjunction
This rule has been drilled into grade schoolers' heads: “Never begin a sentence with and, but, or or.” It turns out there’s no rule against doing so. According to Oxford Dictionary Myth Debunkers, “The argument against using a preposition to introduce a sentence is that such a sentence expresses an incomplete thought (or ‘fragment’) and is therefore incorrect.” But if it has a subject and predicate (as in “And then I went home.”) it’s a sentence. If it doesn’t (“and then home”) it’s not.
Using 'since' when you mean 'because'
Any good writer knows that since refers to time, and because refers to cause, right? Not quite. Although this distinction is specified in many style guides, so many people continue to misuse the word since that dictionaries have now expanded its definition to include because. So consider the two words “partially” interchangeable: Only use since in place of because if it’s not ambiguous. For instance, it’s unclear whether since refers to time or cause in this sentence: “Since I’ve had insomnia, I’ve been cranky.”
Splitting an infinitive
Some call this one the “Shatner rule.” Many grammarians consider Captain Kirk’s statement “to boldly go where no man has gone before” incorrect because it’s a “split infinitive”— wherein an adverb is inserted between to and the verb. This rule has no foundation, though. It was made up in the 1800s, probably by linguists who compared our language to Latin, which doesn’t allow for split infinitives. But English is different— take, for example, “Uncle John decided to gradually get rid of the beer in our office that we tap into during meetings.” Moving gradually anywhere else in the sentence changes the meaning. In this case, the split infinitive can’t be avoided.
Using 'while' to mean 'although'
According to Eric Partridge in Usage and Abusage, using while in place of although “is a perverted use of the correct sense of while, which properly means ‘at the same time.’” It can also cause confusion, as in this example: “While you were still learning to tie your shoes, I was able to solve this complex math problem.” Does the speaker mean although the person was learning to tie their shoes, or at the same time the person was learning to tie their shoes? So don’t use while if it muddles the meaning of what you’re trying to say, otherwise it’s okay.
Using passive voice
Teachers and editors often insist that writers use an active voice to identify who or what is acting in every sentence. Sometimes students are assigned to craft an entire story in an active voice, with no forms of the passive be verb (such as am, was, or has been). That’s sound advice, but not a set rule. It’s all about what mood the writer is trying to convey. For example, ending a story about a party by writing “Everyone had a good time” (active voice) might not be as strong as ending with “A good time was had by all” (passive voice).
Using 'over' when you mean 'more than'
Historically, over was reserved to mean “higher than,” referring to the physical proximity of objects to one another. More than meant “a greater amount than.” For the last century, though, people have mistakenly used over in the numerical sense: “She made over a million dollars.” In 2014 the editors at the Associated Press finally relented: “New to the Stylebook: over, as well as more than, is acceptable to indicate greater numerical value.” (Note: We sent this one to our copy editor, who protested with “more than my dead body!”)
Using 'which' for 'that' as a relative pronoun
The rule goes: “Only that should introduce a restrictive clause—a clause that isn’t preceded by a comma and contains information crucial to the sentence’s meaning. Which should introduce clauses that are set off by a comma.” Both of these are correct: “Jay discovered the duck that Uncle John had stolen.” and “Jay discovered the duck, which Uncle John had stolen, in the bathtub.” Yet some experts, including the editors of England’s Cambridge Grammar of the English Language, insist that the rule has no basis. In their view, it’s okay to say, “Jay found the duck which Uncle John had stolen.” However, most American style guides specify that which can be substituted for that only in British English. So Yanks should do it the American way.
Using 'like' in place of 'as'
According to the Chicago Manual of Style, “Increasingly (but loosely) today in ordinary speech, like displaces as or as if as a conjunction to connect clauses. For example, in ‘it happened just like I said it would happen,’ like should read as.” They continue: “Although like as a conjunction has been considered nonstandard since the seventeenth century, today it is common in dialectal and colloquial usage.” Our editors follow the advice in Jack Lynch’s Guide to Grammar and Style, “In formal writing, avoid using like as a conjunction.”
Ending a sentence with a preposition
Experts say: Don’t end a sentence with a preposition (on, off, with, about, etc.), arguing that the term derives from a Latin word meaning “to place before.” Oxford Myth Debunkers says that in Latin, “a preposition should always precede the prepositional object that it is linked with—it is never placed after it.” However, this “rule” wasn’t applied to English until 1672. Later, grammarian Charles Allen Lloyd called it a “groundless notion...no textbook supports it, but apparently about half of our teachers of English go out of their way to handicap their pupils by inculcating it.” So is it okay for you to end a sentence with a preposition? Sure, as long as it still makes sense. Or, as (legend has it) Winston Churchill shot back to an editor who changed one of his sentences to end with a preposition, “This is the sort of nonsense up with which I will not put!”
Omitting the comma after 'Hi' or 'Hello'
Is the first comma in “Hi, Mom,” necessary or superfluous? It used to be commonplace to begin a letter home with “Dear Mother.” As English became less formal in the 20th century, it became “Hello, Mom,” with a comma following hello. Since the advent of e-mail and texts, communication has relaxed so much that people simply write “Hi Mom.” So in casual greetings, you can leave it off. However, according to the Chicago Manual of Style, “If you’re writing to a client or your boss...that means putting a comma before the direct address (Hi, Fred).”