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What's It Worth? A Confusing Use of the Apostrophe

I asked fellow editors recently what usage rule they wanted to know more about or what rule they saw broken regularly. I received lots of answers (thanks, all!), including this one:

Why is worth preceded with a possessive noun or pronoun, as in two days' worth?

We can include similar phrases in the question, such as for goodness's sake. Can day or goodness possess something? What does it mean to possess sake?

Changing Terminology

The problem starts with our understanding of what we use the apostrophe for and what possession is. This misunderstanding isn't new; it begins with 18th-century grammarians (yes, those gents again).

The term possessive was introduced into the grammar lexicon by Bishop Robert Lowth in 1762 in A Short Introduction to English Grammar. Lowth used it to replace the older term, genitive:

The relation of Possession, or Belonging, is often expressed by a Case, or a different ending of the Substantive. This case answers to the Genitive Case in Latin, and may still be so called; though perhaps more properly the Possessive Case. Thus, "God's grace:" which may also be expressed by the Preposition ; as, "the grace of God." It was formerly written Godis grace : we now very improperly always shorten it with an Apostrophe, even though we are obliged to pronounce it fully ; as, " Thomas's book :" that is, " Thomasis book " not " Thomas his book," as it is commonly supposed.

Other grammarians and language commentators did the same, and collectively we soon forgot that the genitive is about more than possession.

Losing the Broader View

Longman's Grammar of Spoken and Written English divides the genitive into specifying genitives (e.g., possession, as in Thomas's book) and classifying genitives, two of which are the genitive of time (a summer's day) and the genitive of measure (two weeks' worth). Instead of "whose …?" classifying genitives commonly answer the question "what kind of …?"

Longman's notes that classifying genitives are more closely related to adjectives than determiners (e.g., the). According to the text, a classifying genitive:

  1. Can't be replaced by a possessive determiner: children's clothing department vs. their clothing department
  2. Can follow a determiner and whole-phrase modifiers: the children's department, Sears's children's department
  3. Forms a unit with the noun that follows it, preventing an adjective from coming between them: a large children's department vs. a children's large department
  4. Is often rewritten as a for phrase rather than an of phrase: department for children vs. department of children

Because those early grammarians switched from using genitive to possessive, they got into the mindset that possession was the genitive case. That led to rules like "Don't attribute possession to something inanimate." Phrases such as two weeks' worth and for goodness's sake aren't supposed to be possible. Yet there they are. In common usage.

Google Books records them to at least 1800:

Correcting Ourselves

Because we've narrowed our thinking of the genitive case to the possessive case, we often forget to use the apostrophe in such phrases as two days' worth and for goodness's sake. Longman's prefers the view that language users are choosing between a genitive case and a common case: two days' worth or two days worth.

Yet we generally don't make this mistake with nouns that don't already end in s:

It's more likely that many language users don't know the genitive is used for more than possession and aren't clear on how to use an apostrophe, which I outlined in "Punctuation Point: Possessing the Apostrophe." Options for how to use the apostrophe with a word that ends in /es/ muddy the waters further.

Whatever the reason for our errors, worth, sake, and related phrases do use an apostrophe to make what we commonly call a possessive case but what is actually another of the genitive cases. It's correct to write:

For goodness's sake, I have two days' worth of work to do after just one vacation day!


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Erin Brenner is the founder of Right Touch Editing, a customizable editing service. She has been an editing professional for over 15 years and is sought after for her expertise in language mechanics. She works on a variety of media in all levels of editing. In addition, she provides bite-sized lessons to improve your writing on her blog The Writing Resource and is the editor of Copyediting.com, which offers advice and training for those who edit copy. Follow her on Twitter at @ebrenner or on Facebook. Click here to read more articles by Erin Brenner.

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Comments from our users:

Tuesday August 5th, 2:06 AM
Comment by: Beuford K.
Thank you for the time you have taken to explain this subject for us. It would be nice to find an nice book that would be affordable and which lays out grammar in easy to understand way

Beuford Kidd
Tuesday August 5th, 5:32 AM
Comment by: Erin B. (Haverhill, MA)Visual Thesaurus Contributor
You're welcome, Beuford. Grammar is complex, so books about it tend to be either equally complex to give you accurate information or overly simple to make it easy to understand but missing lots of information.

Two that are middle of the road that you might check out are Writer's Digest Grammar Desk Reference ( http://amzn.com/B005KWMSQC)and A Practical English Grammar ( http://amzn.com/0194313425). Neither will cover everything, but they'll give you the basic structure of English grammar.

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