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

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:

  • Man Alright After Crocodile Attack” (“Alright” should be “All Right”)
  • This Line Ten Items or Less” (“Less” should be “Fewer”)
  • Auction at This Sight: One Week” (“Sight” should be “Site”)
  • Violent Storm Effects Thousands” (“Effects” should be “Affects”)

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. 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.
Absorb / Adsorb
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:
This product claims to absorb excess dietary fat.
Once the bacteria adsorb to the aluminosilicate mineral surface, they secrete organic molecules.
Accept / Except
“Accept” is a verb meaning “receive with consent”:
Paraguay did not accept the proposed treaty.
“Except” is sometimes a verb (meaning “exclude”) but it is more commonly used just as the word “but” is used:
We could verify all of the important factors except one.
Accurate / Precise
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:
The accuracy of the test results was verified by running 50 of the samples a second time.
This particular scale is accurate to the nearest kilogram.
“Precise” means marked by a high degree of exactitude:
One pint is precisely 568.245 milliliters.
In the simplest terms, accuracy is about conformity to truth or fact, while precision is about exactness.