Common Word Usage Problems  单词使用常见问题 (来源：英语杂志 http://www.EnglishCN.com)

The following list discusses words that present a variety of problems to writers. Reviewing it from time to time will keep you alert to possible usage issues in your own writing.

aggravate Aggravate is used chiefly in two meanings: "to make worse" ("aggravated her shoulder injury," "Their financial condition was aggravated by the fall of the stock market") and "to irritate, annoy" ("The president was aggravated by the Russians' response"), but the latter is rarely seen in writing. However, aggravation usually means "irritation," and aggravating almost always expresses annoyance.

ain't Ain't is avoided in formal writing. But it is widely used in ordinary speech and writing to catch attention and to emphasize ("The fact is, he just ain't going to cooperate"). It often occurs in standard phrases ("If it ain't broke, don't fix it"), and it's used among friends in relaxed conversation ("I ain't gettin' any younger," "There ain't a chance of getting tickets tonight").

amount, number Number is normally used with nouns that can form a plural and can be used with a numeral ("a large number of orders"). Amount is mainly used with nouns that denote a substance or concept that can't be divided and counted up ("the annual amount of rainfall," "a large amount of money"). The use of amount with count nouns ("a substantial amount of job offers") is usually regarded as an error.

apt, liable, likely Both liable and apt, when followed by an infinitive, are used nearly interchangeably with likely ("liable to get tired easily," "The roads are apt to be slippery," "It's likely to be hot tomorrow"). In writing, liable is generally used only for situations risking an undesirable outcome ("If you speed, you're liable to be caught").

as, as if, like Like has been used as a conjunction in the sense of as ("just like I used to do") and as if ("It looks like it will rain") for nearly 600 years. However, these uses are often criticized, and it is safer to use as or as if instead ("just as I used to do," "It looks as if it will rain").

as far as "As far as clothes, young people always know best" is an example of as far as used as a preposition, with the meaning "as for" or "regarding." This use, which developed from the traditional conjunction use ("As far as clothes are concerned, . . ."); is very common in speech but is usually regarded as an error in writing.

awful, awfully Awful has long been acceptable in the meanings "extremely objectionable" ("What an awful color") and "exceedingly great" ("an awful lot of money") in speech and casual writing. Both awful and awfully are used as intensifiers in informal speech and writing ("I'm awful tired," "He's awfully rich") but are rare in more formal contexts.

between, among It is often said that between can only be used when dealing with two items ("between the two trees"), and that among must be used for three or more items ("strife among Croats, Serbs, and Muslims"). However, between is actually quite acceptable in these latter cases, especially when it applies to one-to-one relationships ("constant disagreements between the three of us").

but There is no reason why sentences should not begin with but ("But now we come to the difficult part"). But, as a preposition with the meaning "except," may be followed by a pronoun in the either the nominative or the objective case ("No one but I [me] could solve the puzzle"), but the objective case is always used when it is part of a noun phrase serving as an object ("He looked at everyone but her"). A less common use of but is as an adverb meaning "only" ("Had they but known, they could have saved themselves").

can, may Can, unlike may, is used to indicate the power to do something ("He can lift 200 pounds"). To denote possibility, both can and may are used ("The problem can [may] be solved in two different ways"). To denote permission to do something, can is common in informal speech ("She's told her kids they can stay up till 10:00 tonight"), but may is preferred in writing. However, in negative statements, cannot and can't are more common than may not ("The generals can't act unless the president tells them to").

comprise The sense of comprise meaning "to compose or constitute" ("the branches that comprise our government") rather than "to include or be made up of" ("Our government comprises various branches") has been attacked as wrong, for reasons that are unclear. Until recently, it was used chiefly in scientific and technical writing; today it has become the most widely used sense. But it still may be safer to use compose or make up instead.

data Data today has a meaning independent of its use as the plural form of datum. It is used in one of two ways: as a plural noun (like earnings) that takes a plural verb and plural modifiers (such as these or many) but not cardinal numbers ("These data show that the recession ended in March"); or as an abstract mass noun (like information) that takes a singular verb and singular modifiers such as this, much, or little ("The data on the subject is plentiful"). Both constructions are standard, but the plural form is more common in print. Avoid using signs of the singular (like this or much) when you use a plural verb.

different from, different than Both of these phrases are standard; however, some people dislike different than and will insist that, for example, "different than the old proposal" be changed to "different from the old proposal." Different than works best when a clause follows ("very different in size than it was two years ago").