I must confess that I do not myself observe the distinction between “that” and “which.” Furthermore, there is little evidence that this distinction is or has ever been regularly made in past centuries by careful writers of English. However, a small but impassioned group of authorities has urged the distinction; so here is the information you will need to pacify them.

If you are defining something by distinguishing it from a larger class of which it is a member, use “that”: “I chose the lettuce that had the fewest wilted leaves.” When the general class is not being limited or defined in some way, then “which” is appropriate: “He made an iceberg Caesar salad, which didn’t taste quite right.” Note that “which” is normally preceded by a comma, but “that” is not.

Comments on this issue by Jack Lynch.

Back to list of errors

BUY THE BOOK!

To find the mean (or average) of a series of numbers, for example 1,2,3,4,5 & 6, add them all together for a total of 21; then divide by the number of numbers (6) to give the mean (or average) of 3.5.

In contrast, when half the data of a set are above a point and half below, that point is the median. The difference between mean and median can be quite significant, but one often sees the terms used wrongly even in technical contexts.

Back to list of errors

BUY THE BOOK!

Apple’s Macintosh computers are usually referred to as “Macs” for short. Windows users unfamiliar with the usual way of rendering the name often write it as if it were an acronym, in all caps: “MAC.”

But a MAC is something quite different. Every computer on a network has a Media Access Control number; so when your IT support person asks you for your “MAC address,” don’t say you don’t have one just because you use Windows. Don’t ask me how to find the MAC address for your Windows computer though; I’m a Mac user.

Back to list of errors

BUY THE BOOK!

“Into” is a preposition which often answers the question, “where?” For example, “Tom and Becky had gone far into the cave before they realized they were lost.” Sometimes the “where” is metaphorical, as in, “He went into the army” or “She went into business.” It can also refer by analogy to time: “The snow lingered on the ground well into April.” In old-fashioned math talk, it could be used to refer to division: “Two into six is three.”

In other instances where the words “in” and “to” just happen to find themselves neighbors, they must remain separate words. For instance, “Rachel dived back in to rescue the struggling boy.” Here “to” belongs with “rescue” and means “in order to,” not “where.” (If the phrase had been “dived back into the water,” “into” would be required.)

Try speaking the sentence concerned aloud, pausing distinctly between “in” and “to.” If the result sounds wrong, you probably need “into.”

Then there is the 60s colloquialism which lingers on in which “into” means “deeply interested or involved in”: “Kevin is into baseball cards.” This is derived from usages like “the committee is looking into the fund-raising scandal.” The abbreviated form is not acceptable formal English, but is quite common in informal communications.

See also turn into.

Back to list of errors

BUY THE BOOK!

These two words, which originally had quite distinct meanings, have become so blended together that most people no longer distinguish between them. If you want to avoid irritating the rest of us, use “imply” when something is being suggested without being explicitly stated and “infer” when someone is trying to arrive at a conclusion based on evidence. “Imply” is more assertive, active: I imply that you need to revise your paper; and, based on my hints, you infer that I didn’t think highly of your first draft.

“Impertinent” looks as if it ought to mean the opposite of “pertinent,” and indeed it once did; but for centuries now its meaning in ordinary speech has been narrowed to “impudent,” specifically in regard to actions or speech toward someone regarded as socially superior. Only snobs and very old­fashioned people use “impertinent” correctly; most people would be well advised to forget it and use “irrelevant” instead to mean the opposite of “pertinent.”

Back to list of errors

BUY THE BOOK!

Video created by NBC:

The “-oid” ending in English is normally added to a word to indicate that an item is not the real thing. A humanoid is not quite human. Originally “factoid” was an ironic term indicating that the “fact” being offered was not actually factual. However, CNN and other sources took to treating the “-oid” as if it were a mere diminutive, and using the term to mean “trivial but true fact.” As a result, the definition of “factoid” is hopelessly confused and it’s probably better to avoid using the term altogether.

Back to list of errors

BUY THE BOOK!

Those bright flashes in the storm clouds indeed used to be referred to as “lightening,” later as “light’ning,” but now they are simply “lightning.”

“Lightening” has a quite different meaning in modern English: making lighter, as in lightening your load or lightening the color of your hair.

Back to list of errors

BUY THE BOOK!

Quite a few people accidentally say they want to make some process “less painless” when they mean “less painful.” “Less painless” would be more painful.

Back to list of errors

BUY THE BOOK!

Myths are generally considered to be traditional stories whose importance lies in their significance, like the myth of the Fall in Eden; whereas legends can be merely famous deeds, like the legend of Davy Crockett. In common usage “myth” usually implies fantasy. Enrico Caruso was a legendary tenor, but Hogwarts is a mythical school. Legends may or may not be true.

But be cautious about using “myth” to mean “untrue story” in a mythology, theology, or literature class, where teachers can be quite touchy about insisting that the true significance of a myth lies not in its factuality but in its meaning for the culture which produces or adopts it.

Back to list of errors

BUY THE BOOK!

There are quite a few words spelled with a double L in UK English which are spelled in the US with a single L. Examples include “woollen” (US “woolen”), “counsellor” (US “counselor”), “medallist” (US “medalist”), “jeweller” (US “jeweler”), “initialled” (US “initialed”), “labelled” (US “labeled”), “signalled” (US “signaled”), “totalled” (US “totaled”).

Most of these won’t cause Americans serious problems if they use the UK spelling, and a good spelling checker set to US English will catch them. But “chilli” looks distinctly odd to Americans who are used to spelling it “chili” when it turns up in the UK-influenced English of South Asian cookbooks. (Of course Spanish speakers think it should be chile.)

Back to list of errors

BUY THE BOOK!