I have been posed with a question in an economics class at college which I cannot decipher: "Explain how an increase in the price level affect the real value of money. Give a real world example."

I emailed the instructor to ask for clarification, asking if he missed a plural somewhere or made a typo, and he advises me as follows: "It is not missing a plural – simply read it as price level affects."

Would it written as “Price level affects” not be plural? Is it possessive rather than plural? Slippery slope? I want to write him back, but worry I may not truly have a full grasp of the grammar and English complexities involved. Is there is some grammatical rule I do not know which dictates that words (or specifically, the word affect) no longer need to be made plural to be read as plural? Is adding an "s" to affect to make it affects in this case not making it plural? What am I missing?

  • 1
    Subject increase in price (singular) will take a plural verb 'affects.' Indeed, there's a grammatical error.
    – Andy Semyonov
    Apr 18, 2018 at 6:28
  • 1
    Your professor is telling you he messed up the verb, not the noun. So it's not a plural noun (price levels affect), the verb should agree, but doesn't, with the singular noun (price level affects). So he wants you to answer the question for price level, not price levels.
    – jimm101
    Apr 19, 2018 at 18:43
  • Doubletalk: “I didn’t make a mistake, but what I meant to say was ‘…’.” Apr 20, 2018 at 23:36

4 Answers 4


The mistake in your instructor's sentence is one of concord or agreement. The singular noun increase does not 'agree' with the verb affect, since the third person singular verb requires an -s: affects.

So, it needs to be how increases ... affect or how an increase ... affects. There is no possessive in the sentence.

That said, I don't think you have anything to gain by writing back to him. He has already indirectly admitted his error.

  • Does that imply OP is dealing with a 'greater than thou' instructor? :)
    – Andy Semyonov
    Apr 18, 2018 at 6:47
  • @AndySemyonov. In my experience of instructors, most are happy to engage in substantive discussions about the requirements of a task. Rather fewer, however, are happy to have simple typos belaboured by students who want to show off their superior grammatical knowledge. But in no way am I implying that the instructor in this case is one such typical instructor or that the OP is one such student!
    – Shoe
    Apr 18, 2018 at 6:59
  • You're probably correct that I don't stand much to gain by responding, I am just bothered by the issue that he's placing the "blame" on me for not being able to translate his poorly constructed question - as if I have a reading comprehension problem while he assumes no responsibility for having made a mistake. He refuses to edit. His response was brusque, the tone was speaking down to me. Mostly I just wanted to know about the complexities of agreement (which I didn't know the name for until now - I just knew his sentences was wrong, but not how), which you explained perfectly, so thank you!
    – Phaewryn
    Apr 18, 2018 at 17:13
  • And there I go typoing similarly in the comments (but at least I can admit it). Onto my work for the day, feeling slightly vindicated thanks to StackExchange! Thanks everyone.
    – Phaewryn
    Apr 18, 2018 at 17:21
  • @Phaewryn. I entirely agree that the response to you was brusque. It was partly for that reason that I felt he probably would not want to engage further on the matter. All things told, it's best not to get on the wrong side of your instructor unless a real issue of principle is involved.
    – Shoe
    Apr 18, 2018 at 17:24

Firstly "affect" is a verb. It is neither plural or possessive. Those are attributes of nouns associated with a verb.

The subject here is "an increase in the price level" which is singular. If nothing else, the article "an" makes this clear.

The sentence should thus use the verb in the form "affects" (3rd person active singular subject). If; however, you prefix it with "would" then "affect" is correct.

  • Thank you. I knew I was missing something, but not what, exactly, and when you google "grammar affect" all you get are the differences between affect and effect, so I was quite stuck! Thanks again!
    – Phaewryn
    Apr 18, 2018 at 17:15
  • Yes. Too much use of the word affect can make you sound affected. Apr 18, 2018 at 21:58
  • So verbs can't be singular or plural? Apr 20, 2018 at 23:34
  • Sort of. As actions they can be continuous, repeated or of a single point of time, which is a bit like single/plural but not for the purpose of counting; the distinction is one of their temporal nature. Apr 21, 2018 at 4:26
  • The cat plays; the cats play.  The verb changes form based on number; see subject-verb-agreement and EL&U’s verb-agreement tag. Apr 21, 2018 at 17:36

In this context - indeed in any context - affect is a verb: not a noun. It is not a plural. It is simple present tense, like "influences". "Explain how an (something) influences (something else)"

The noun is "effect".

  • You were right the first time; in this context, "affect" is a verb. In other contexts, e.g., psychology, the word can be used as a noun. (This use is relatively rare but is recognized by various dictionaries.) Apr 18, 2018 at 20:36

Affect in this sentence is a verb so, it makes sense if we say - an increase in the price level affects/reduces the real value of money. It is not plural or possessive. The verbs affect is in the present simple tense. You may also say - an increase in the price level will affect the real value of money.

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