When I woke up this morning my girlfriend asked me, "Did you sleep good?” I said, "No, I made a few mistakes.”

This chapter is for everyone. We have all made the mistakes described herein. How many times have you found yourself puzzling over the distinction between "affect” and "effect,” "it’s” and "its”? It is not surprising that we maintain such uncertainties, because in any town in America you can find billboards and road signs and ads and newspapers with outright usage errors such as these printed boldly for all to see:

Perhaps there is little need here to preach about the value of the material in this chapter. Quite simply, in formal writing, conventions have been established to aid us in choosing the best term for the circumstances, and you must make it your business to learn the rules regarding the trickiest and most misused terms. You can also dig up style handbooks with recommendations on using tricky terminology within your discipline. For instance, Geowriting: A Guide to Writing, Editing, and Printing in Earth Science, by Robert Bates, gives advice on using such terms as "areal," "lithology," "terrane," and "zone"; medical students can turn to The Aspen Guide to Effective Health Care Correspondence or Writing, Speaking, and Communication Skills for Health Professionals for advice on commonly used contractual terms including "yellow-dog contract" and "apostolate." If you do not mind investing about 40 bucks, you could purchase The Chicago Manual of Style, essentially a bible for book publishers, which answers almost every conceivable style question. Finally, recognize that companies and institutions often develop their own style guides for internal use to address common issues. As an example, my home institution of Penn State publishes an Editorial Style Manual, which addresses local style issues related to such things as campus building names and academic titles. Never hesitate to look up a term for its proper usage if you are uncertain—there is a lot to be said for being correct.

I decided to include these terms because they are used so commonly in science writing, and because even though the spell checker and grammar checker do not distinguish between them, the thinking student obviously must do so. "Absorb," which describes a general process, means "to soak in." A more specialized term, "adsorb" describes the surface of a solid or liquid accumulating gas, vapor, or dissolved matter:

“Accept” is a verb meaning “receive with consent”:

“Except” is sometimes a verb (meaning “exclude”) but it is more commonly used just as the word “but” is used:

As your cleverest professors might be fond of saying: "A measurement can be accurate without being precise; a measurement can be precise without being accurate." A simple demonstration of this distinction: We can refer to a wrapped collection of hay as a bale (an accurate measurement) without precisely counting its strands; we can scatter the hay and number the strands (a precise measurement) but not accurately call it a bale. More to the point, we cannot claim that a particular event occurred "precisely 20,000 years ago" or that a particular ore reserve weighs "precisely 1 million tonnes"; by definition, such values are measured coarsely rather than exactly. In relation to the weather, we would properly refer to an accurate (true) forecast, but a precise (exact) temperature.

"Accuracy" denotes how closely a measurement approaches its true value. An accurate measure, then, is one that conforms well to an implied or stated benchmark:

"Precise" means marked by a high degree of exactitude:

In the simplest terms, accuracy is about conformity to truth or fact, while precision is about exactness.

You are not alone if you commonly confuse "affect" and "effect." These two terms were confused in print as early as 1494. The key to correct usage here is to determine whether the term is being used as a noun or verb, and to discern the intended meaning.

"Affect" is usually used as a verb. (I think of the "a" in "affect" standing for "active verb.") To "affect" is to "influence":

"Effect" is usually used as a noun, and it means "outcome or result":

Finally—to the horror of many—"effect" can also be used as a verb to mean "to bring about," as in the phrase "to effect a change," while "affect" can be used as a noun (usually in psychology) to mean "conscious subjective emotion." Such usages, though infrequent, highlight why you must be particularly careful to choose the correct term for the circumstances, keeping in mind both the intended meaning and the intended part of speech.

"Alot" is never correct. It is supposed to be two words—therefore: "a lot." Never write a note to your composition professor at the end of the semester assuring her that you "really learned alot."

"Allot" is to "assign a portion to":

All wrong. “Alright” is listed in most dictionaries as a common misspelling of what should be two words. In your writing, use “all right”:

As an adjective, “alternate” means “every other,” and it is usually used in relation to time or objects:

“Alternate” is also a verb, meaning “to switch back and forth in turns”:

“Alternative” denotes that a choice was made between at least two things:

“Among” is appropriate to describe broad relationships when more than two things are involved:

“Between” is used to describe specific relationships involving only two things:

Current usage also permits “between” when each entity is considered individually or severally in relation to the others:

“Amount of” works with noncountables; “number of” works with countables:

If you have ever read a lengthy legal document, you have probably encountered an abundant use of "and/or." Nevertheless, in good conscience, I cannot recommend that you use this construction in your writing, because the best style handbooks preach against it and label its use unprofessional. Besides, both "and" and "or" by themselves effectively link ideas that can be considered either individually or collectively. For example, in the second sentence of this paragraph, I used "and" to link "preach against it" and "label its use unprofessional," even though not every style handbook would necessarily do both of these. In other words, "and" can be used to suggest likely combinations of ideas, while "or" can be used to help the reader consider just one idea at a time.

If you feel, as some writers do, that you want to use "and/or" just to be fastidious, instead you should simply word the sentence appropriately to cover the different possibilities:

Use “region” for large geographic units and “area” for smaller ones. Also, keep your usage consistent—the “region” of one paragraph should not become the “area” of another:

“Section” is best reserved for land sections and cross-sections:

These two words are not interchangeable. “As” means “to the same extent, degree, or in the way that”:

“Like” means “similar to”:

Literally, an "aspect" is "the idea of a thought viewed by the mind"—in other words, a "thing." Thus, its value is highly limited; yet many writers produce vacant sentences such as "This paper will deal with many aspects of my topic," or "The problem has many aspects, and the first aspect is the most important aspect." Such sentences simply are not worth the ink (nor the electrons).

If the word "thing" is unacceptable (and it usually is), then "aspect" should be too. When you are tempted to use this word, consider alternatives that carry more specific meaning, such as "principle," "property," "factor," "dilemma," "reason," "part." Use the exact, most direct term that best conveys the sentence meaning.

In meaning, these three verbs seem to be nearly interchangeable; all three denote a certainty or guarantee being made. However, in practice, the best writers do distinguish among these terms, as follows:

“Assure” is used to refer to interaction between people:

“Ensure” is used more broadly to mean “to make certain”:

“Insure” is favored in instances of guaranteeing life or property against risk:

These combinations are not interchangeable, but many writers mistakenly combine “between” with “to” and “from” with “and.” When defining two or more end parameters, “between” is most effectively linked with “and”; “from” most effectively linked with “to” (and more than one “to” may be used in a series of linked terms or phrases):

Also, the hyphen between two values (such as “5-10”) functions invisibly as the word “to” or “through,” but it should only be used alone. Therefore, “It moved 5-10 meters” is correct, while “It moved from 5-10 meters” or “It moved between 5-10 meters” is not.

These two prefixes create some confusion, because they both mean “occurring twice during.” By convention, a writer can correctly use “bimonthly” and “semimonthly” to mean either “twice a month” or “once every two months.” To avoid confusion, I recommend that you follow these standard usage practices:

If confusion still might result in context, avoid using the prefixes and simply write out the time-frame clearly (“every two weeks”; “twice per month”).

Both “can” and “could” are best used to express factual possibility and scientific likelihood. As opposed to “may” and “might,” which imply permission or human interpretion, “can” and “could” emphasize capacity and likelihood:

“Cite” is a verb meaning “to mention” or “to make reference to”:

“Site” is a noun meaning “location”:

“Sight” is both a noun and a verb that refers to seeing:

"Coarse" means "of low quality, not fine in texture." The most common meanings for "course" are "a curriculum unit" or "the direction of continuing movement":

Use "compared to" to point out similarities between things:

Use "compared with" when noting both similarities and differences:

For further discussion of usage issues related to making comparisons, see Grammar Girl's handy "Between, Compared to, and Compared with" discussion.

One could argue that most writers confuse these terms as an error of spelling rather than usage—all the more reason to distinguish between them carefully and avoid an embarrassing, sloppy habit. The distinction is simple: "complement" (note the "e" in the middle) means "something that completes"; "compliment" (note the "i" in the middle) means "to express praise" or "thanks to":

Spelling "complement" correctly is especially important in fields such as biochemistry, where "complement components" and "complement pathways" are cited frequently.

To "compose" or "constitute" is "to form" or "to make up":

"Include" indicates a selective, incomplete listing of constituents, implying the presence of other constituents as well:

Literally, "to comprise" is "to include" or "contain." The earth comprises rocks (it includes them), but rocks do not comprise the earth (they do not include it). Therefore:

Strict writers say that using "comprise" in the passive ("One foot is comprised of 12 inches") is unacceptable; instead, use "is composed of" or "is made up of."

"Continual" describes intermittent activity; "continuous" denotes unceasing, uninterrupted activity. Meals are continual; time is continuous:

Established usage dictates that “different than” is not correct; good writers use “different from”:

These two phrases are both too wordy and too colloquial for formal writing. They also fail to express a simple causal relationship with efficiency. Handily, these phrases can usually be replaced by the word "because":

It is important to use these abbreviations literally and to punctuate them correctly. Many writers confuse "e.g." and "i.e.," and many type "et al." improperly or do not properly recognize what words it represents.

The abbreviation "e.g." is from the Latin exempli gratia and means, literally, "for example." Periods come after each letter and a comma normally follows unless the example is a single word and no pause is natural:

The abbreviation "i.e." is from the Latin id est, meaning "that is." Loosely, "i.e." is used to mean "therefore" or "in other words." Periods come after each letter and a comma normally follows, depending on whether the wording following the abbreviation dictates a natural pause:

The phrase "et al."—from the Latin et alii, which literally means "and others"—must always be typed with a space between the two words and with a period after the "l" (since the "al." is an abbreviation). A comma does not follow the abbreviation unless the sentence’s grammar requires it. Some journals italicize the phrase because it comes from the Latin, but most do not.

Never begin a sentence with any of these three abbreviations; if you want to begin a sentence with "for example" or "therefore," always write the words out.

This abbreviation means, literally, “and other things.” Many professors urge against using etc. in formal writing because it is, by definition, nonspecific, but it can be used effectively when you have responsibly chosen representative constituents in order to avoid a cumbersome list:

Tacking on “etc.” at the end of a list introduced by “for example” or “such as” is sloppy, because “for example” suggests that you have already carefully selected and presented the key constituents, which the “etc.” then undermines. Good alternatives to “etc.” are “for example,” or “such as” followed by just a few concrete representative examples that best demonstrate your point.

Use “fact” only in reference to matters capable of being proven; do not use it in matters of subjective judgment:

Use “factor” literally to describe a relationship in which one thing is an actual agent for another thing:

Depending on the context, generally acceptable synonyms for factor are “element,” “ingredient,” “component,” and “constituent.”

"Farther" is used literally to describe matters of measurable distance (I think of the imbedded word "far," suggesting distance); "further" is more figurative and is used for broader general comparison:

Both these words are adjectives, but "few" is usually used to describe countable nouns while "less" is used to describe noncountable nouns. Countable nouns are often physical whereas noncountable ones are often abstract or nonphysical:

If you memorize the phrase "few units = less quantity," you will remember the distinction—"few" is for countables occurring in units, while "less" is for noncountables occurring in quantity.

As often happens in English, exceptions do arise. Sentences involving periods of time, sums of money, or specific measurements usually require "less":

These two words, sometimes used in combination, are often misused in technical writing. "Former" refers back to the first of two things mentioned; "latter" refers back to the second of two things mentioned:

When more than two members of a list are involved, or when the sentence’s context does not clearly indicate an antecedent (a word or phrase being referred back to), then strictly avoid using "former" and "latter."

These two words are too often used interchangeably, but they are completely different in meaning. "Imply" means to suggest or to indicate; "infer" involves a person actively applying deduction:

Another way to look at it: We can substitute "suggest" for "imply" and "reason" for "infer," still retaining the correct meaning.

This phrase is virtually meaningless, but we often hear it on the news and in bloated speeches. "In terms of" is really just a wordy and sloppy transition—usually an unoriginal disguise for a simple preposition, such as "in," or a more elegant phrasing, such as "in relation to." "In terms of the cost, it is high," is easily revised to "Its cost is high." Do not use "in terms of," or do so trembling.

“Irregardless” is just wrong—an invented word. Use “regardless”:

These two words probably represent the most common usage problem in papers, but the distinction between the words is painfully simple. "It’s" always means "it is." "Its" never does. At first glance, there seems to be an inherent inconsistency, because we usually use apostrophes to indicate possession, but certain words, for instance "its," "hers," and "yours," automatically show possession and need no apostrophes. When you write "it’s" be certain that you mean two words rather than one. Read it to yourself aloud if you have to, reading every "it’s" as "it is."

"Lay" (present tense) implies an agent acting on something, and it means "to put, place, or prepare." Its other forms are "laying," "laid" (past tense), and "laid" (with "has," "have," or "had," usually implying a past event that continues into the present):

"Lie" (present tense) means "to recline" or "to be situated," and its other forms are "lying," "lay" (past tense), and "lain" (with "has," "have," or "had," usually implying a past event that continues into the present):

“Lead” is a present tense verb meaning “to guide” or “to direct”. “Led” is the past tense of the same verb, and it must not be spelled with an “a”:

"May" expresses possibility, permission, or human interpretation. "Might" is used in the same way, but implies possibility over permission:

Many writers puzzle between "may" and "can," and I always advise them to elect "may" when human permission or human interpretation (especially speculation) is involved, and "can" when the point is more factual or proven:

It is a shame that many high school teachers continue to penalize students for each occurrence of "one" or "you" in an essay. You certainly are permitted to use these words in writing, but you must do so sparingly, appropriately, and for the reader’s sake. "You" and "your" are somewhat informal but are nevertheless directed explicitly at the reader; thus they are especially appropriate for memos, letters, advice, or a set of instructions designed to apply to the reader in the act of reading:

In more formal, technical documents, rely on the word "one" to refer to people generally, ideally as you present them as potential thinkers or doers:

Finally, be careful not to switch back and forth arbitrarily between "you" and "one"; be consistent and use your common sense.

Literally, "per" means "for every" or "according to":

The phrase "as per" is incorrect—a redundancy.

These two terms are not interchangeable. “Percent” means “per hundred” and can either be written out or expressed by the symbol %. Ideally, “percent” is always associated with a specific number:

“Percentage” is used to refer to a general relationship rather than a specific measure:

In published literature, many writers use “percent” as an adjective (“percent quartz”) for economy, especially in figures and tables. If this is done, the same phrasing should be used consistently to refer to the same thing.

In Geowriting: A Guide to Writing, Editing, and Printing in Earth Science, Robert Bates amusingly notes that "unique, like pregnant and dead, is an absolute: it cannot be more or less." "Unique" means "being the only one of its kind"; "perfect" means "without flaw." Professors reading of "a unique insight" or "a perfect software package" could correctly challenge these absolutes—i.e., the insight would certainly parallel others, and the software package could certainly be improved. By definition, uniqueness and perfection are so rare in scientific contexts that the concepts are best avoided in formal writing. And if you dare to refer to something as "perfectly unique," keep an aspirin handy for your professor.

These two terms are frequently confused, but their meanings are highly different from each other. The most common use of "perspective" is to mean "point of view":

"Prospective" means "expected or likely to happen":

Various forms of "precede" and "subsequent" are often confused with each other, but the two terms are opposites. To "precede" is "to come before"; "subsequent" means "following in time":

"Precede" is also sometimes confused with "proceed," which means to go forward:

In technical writing, avoid the words “pretty,” “quite,” “rather,” and “very” as adjectives. Some writers mistakenly use these words to create emphasis or lend the appearance of exactitude, but this backfires—“the pebble is round” is clearer than “the pebble is quite round.” By definition, these words are nonspecific, and many professors are highly sensitive to their use. Other terms such as “virtually,” “highly,” “essentially,” or “relatively,” may work in their place, but be certain to use these terms literally and sparingly. “Rather” as a comparative word is, of course, valid in an “a rather than b” construction.

These two terms are often confused, but the fact is they have no meanings in common. “Principal” means “first, primary, or main”:

“Principle” implies an abstraction, and it means “a doctrine,” “a truth”:

“Principal,” of course, also denotes the head of a school, and in some fields, “principal” has specialized meaning: in law, a principal empowers another to act as his or her representative; in finance, the principal is the capital of a financial holding as distinguished from the interest.

“Respective” is an adjective, usually meaning “particular”:

“Respectively” means “in the order mentioned,” and is usually preceded by a comma:

The rules governing these two words are a bit flexible, but "which" is too often used where "that" should be. "That" is preferable when you are limiting or restricting a noun:

The following line from a nursery rhyme is instructive here, because all of the "thats" are correct:

In contrast, "which" introduces a phrase that provides descriptive yet incidental information, and "which" often requires commas on one or both ends of the phrase it introduces:

In short, you use "that" to complete a noun and "which" simply to describe a noun.

"Try and" is often used incorrectly to introduce a verb that must be linked with "to." "Try to" is the correct choice:

"Will" suggests strong probability or future likelihood. "Would" implies the same, but is typically used when the probability is more hypothetical.

Be especially careful not to overuse "will" and "would," in particular when affirming facts. Some writers habitually compose sentences such as "A comparison of MWD logs and wire line logs would be difficult because they will operate in different environments." In a revised version of this sentence, the writer should eliminate "will" and "would," simply affirming the fact that she knows to be true: "A comparison of MWD logs and wire line logs is difficult because they operate in different environments."