As a class, prepositions tend to be pretty agreeable. They go where they’re told and do what’s asked of them. But they are persnickety on a few points, such as how and when they are to be paired up with a given verb, whether or not they feel like hanging out alone at the end of a sentence, and how to get other parts of speech to stop barging in on their territory. The following entries represent the most common errors made with prepositions.

Here’s Why: How do you know whether to use “to” or “with”? “Agree to” introduces an infinitive form of a verb such as “to jump,” “to suppose,” or “to annoy.” It means to consent to, as in consenting to fulfill the terms of a contract. “Agree with” introduces a noun. It means to be in accord or alignment with, as in agreeing with a point of view. So in this sentence, where we don’t have an infinitive, and where we’re talking about being on the same side in an argument, “agree with” is correct. Additional correct examples are:

Here’s Why: “Differ from” means to be unlike, as in one dress differing from another. “Differ with” means to disagree with, as in differing with a point of view, which is the case in our example sentence. Additional examples are:

Here’s Why: “Different from” is standard, always acceptable. But there is a range of opinions from usage experts on the appropriateness of “different than.” “Different than” is acceptable to less conservative speakers when it is followed by a clause, as in I felt different than I did the last time I took this medication. (More conservative speakers veto “different than” altogether, and would rephrase such a sentence so that “different from” would be followed by a noun or pronoun.) What’s never a good idea is using “different than” when making a quick, straightforward comparison between two persons or things, as we did in our example. In other words, don’t say A is different than B. Additional correct examples are:

Here’s Why: It is impossible for anything to “center around.” A center is the exact middle of something, so by definition it cannot be around anything else—it would no longer be the center. A thing can center on or in something else, it can be centered by something else, but it can never be centered around.

Here’s Why: The preposition “at” is always unnecessary with “where.” It performs the same job in the sentence by referring to location, which is what the “where” is there for in the first place. The use of “at” in this way is not uncommon, but it is a big tip-off to others that you’re careless.

Here’s Why: Usage experts aren’t unanimous on this one, but there is a widespread belief that the phrase “as to” is more often than not pretentious-sounding clutter. “As to” does have appropriate uses, such as when you want to begin a sentence by putting a lot of emphasis on a word or phrase that would otherwise have to come later. For example: As to his health, we did not inquire for fear of angering him. Or: As to your decision on the highway project, I cannot agree with you. The kind of use of “as to” that is usually frowned on is employing it as a substitute for prepositions—a use that seems irresistible to folks who are trying to sound businesslike or formal but which generally ends up having the opposite effect. The following are some more examples of “as to” replacing a preposition, each paired with a preferred version (note that there is more than one way to improve these; only one option has been selected).

Here’s Why: You don’t need the “of” after off, the way you would after some other prepositions such as “out,” as in he got out of the car. When you’re using “off” simply say he got off the bus, and leave it at that.

Here’s Why: “Over with” is an informal phrase that expresses an intense desire to complete an unpleasant task. If that’s what you mean, go ahead and say it, as in Let’s get this over with or Isn’t Bob’s recitation of his five-book epic poem over with yet? But if you’re simply referring to something as being finished, as is the case with the meeting here, then stick to “over” by itself.

Here’s Why: When using the phrase “type of,” the extra “a” is always unnecessary and incorrect. Just say type of job, type of flower, type of lipstick, plain and simple.