When should a noun that’s used at­tribu­tively to de­scribe an­other noun be plu­ral, and when should it be sin­gu­lar? And when should it be pos­ses­sive, like bak­er’s dozen and when should it be plu­ral pos­ses­sive, like farm­ers’ mar­ket?

In other words, why do we say teach­ers union rather than teacher union? And why do we say wed­ding plan­ner rather than wed­dings plan­ner?

Which of these vari­ants is or are cor­rect?

  1. stu­dent union
  2. stu­dents union
  3. stu­den­t’s union
  4. stu­dents’ union

What about com­mu­nity val­ues ver­sus com­mu­ni­ty’s val­ues?

Please note I am look­ing for a gen­eral rule or at least some tips. These are only ex­am­ples.

Up­date: It seems even na­tive speak­ers fol­low their per­sonal style to write such com­pound words. I won­der why in the IELTS lis­ten­ing sec­tion, the lan­guage learner has to write a spe­ci­fic form and there is no rule for this.

  • And when should it be possessive, like baker's dozen and when should it be plural possessive, like farmers' market? Oct 9 '14 at 3:33
  • If you click on the tag noun adjunct you might find it very helpful. A list of the highest voted questions: english.stackexchange.com/questions/tagged/…
    – Mari-Lou A
    Oct 9 '14 at 5:23
  • There are things that can't be ruled with rigid grammar rules. Sometimes, especially if there are several possibilities, you have to decide on your own and can choose what you prefer. And you can always study what are the most frequent forms of compound nouns.
    – rogermue
    Oct 16 '14 at 9:01
  • I just checked three universities that I attended and found 1, 2, and 4 were in use. :)
    – Joe Murray
    Oct 22 '14 at 1:28
  • @Mari-LouA Restored. Oct 22 '14 at 18:37

Searching the plural possessive form students' union and the plural form students union on Google gives us around 6,580,000 hits while its compound form student union yields 8,470,000 hits. The singular possessive form student's union gets 324,000 hits.

In Google Books (which should be a more reliable source but to my consternation it isn't always the case) we have the following data in ascending order:

  1. a student's union 418 results
  2. a students' union 7,080 results
  3. a students union 7,130 results (BUT these also include the apostrophe form too.)
  4. a student union 43,200 results

The evidence, therefore, suggests that three out of the four forms are more commonly used. The singular possessive form student's union is, however, also grammatically "correct" because you can talk about a single student belonging to a single union, and the possessive apostrophe expresses this concept. But generally speaking, I would give my preference to the last three. There is no hard and fast rule if your school uses the apostrophe in the expression students' union then stick with that. Personally, I would be happy with either student union and students union, without the apostrophe.

Many compound words are nouns formed by two nouns, the first noun is termed an attributive noun or noun adjunct. It is a noun which acts as an adjective and as such, they are not normally pluralized but there are always exceptions, students union is perhaps exemplary. Wikipedia states (emphasis mine)

Noun adjuncts were traditionally mostly singular (e.g. "trouser press") except when there were lexical restrictions (e.g. "arms race"), but there is a recent trend towards more use of plural ones, especially in UK English. Many of these can also be and/or were originally interpreted and spelled as plural possessives (e.g. "chemicals' agency", "writers' conference", "Rangers' hockey game"), but they are now often written without the apostrophe, although decisions on when to do so require editorial judgment. There are morphologic restrictions on the classes of adjunct that can be plural and nonpossessive; irregular plurals are solecistic as nonpossessive adjuncts (for example, "men clothing" or "women magazine" are solecistic to fluent speakers).

A wedding planner is a person who helps plan other people's weddings. If there were two or more then one needs to pluralize the last noun e.g. She hired two wedding planners to help her on the big day!
The same rule applies to longer compounds such as special needs teacher or science fiction writer

At my school there are several special needs teachers
There are many science fiction writers I enjoy reading.

Further examples

  • A user account ---> two user accounts

  • A bookshelf ---> two bookshelves

  • A cookbook (or a cook's book) ---> two cookbooks (or two cooks' books)

  • People's choice award ---> two people's choice awards

  • A women's club (NOT a woman club) ---> many women's clubs

  • A student union---> several student unions

  • A students union ---> some students unions

@Mr. Shiny and New 安宇 answers a similar question User’s Guide vs Users’ Guide and offers this succinct explanation

User's guide: A guide belonging to one user.

Users' guide: A guide belonging to all the users.

  • I might have to update those figures, since then I've cottoned onto the fact that Google tends to predict overly enthusiastic hits. But if I do...
    – Mari-Lou A
    Jul 6 '17 at 20:40

When we use certain nouns "as adjectives" (clothes, sports, customs, accounts, arms), we use them in the plural form:

clothes shop, clothes shops sports club, sports clubs customs duty, customs duties accounts department, accounts departments arms production.

and when I google "teacher union", the results vary from "teacher union" to "teachers' union" and "teachers union". so I think there's no particular rule for this.


What you have here is two different rules interacting with each other in weird ways. In the first, you have compounds versus noun phrases, and in the other you have ownership versus noun modification.

I can tell you that, when the two nouns form a compound, the noun cannot be inflected. The example that best describes this rule would be wedding planner. One heuristic for compound nouns is to test where the primary stress falls. If if falls on the first noun, it's a compound. If it falls on the final noun, it's an noun phrase. For example, in:

wedding planner

The primary stress falls on wedding instead of planner. If it were an adjective, primary stress would fall on planner. (Think of the distinction between black bird and blackbird.) Here's an overview on English compounds.

As for ownership versus noun modification, this seems to be a distinction between generic and specific. Take, for example, community values and community's values. Where the first would be a compound indicating a generic idea of community, the other would be a phrase referring to the values of a specific community (and should probably be preceded by a determiner).

This distinction between generic and specific can also be made in baker's dozen and farmers' market. Both are noun phrases, but baker is being used in the generic sense (it doesn't matter which baker you talk to, a baker's dozen remains the same), whereas a farmers' market is looked at as a collective (individual farmers selling their products). The same can be said for student union versus students' union. While the student union is a building at my university where generic students are meant to congregate, the students' union is a union of students collecting to advocate for their rights.

  • I say this is an excellent answer, but for the fact that it's got its basics flawed. I need both motorcycle engine as well as motorcycle's engine to communicate effectively.
    – Kris
    Oct 22 '14 at 12:23
  • Sure. My motorcycle's engine happens to be a motorcycle engine.
    – Oldcat
    Oct 22 '14 at 17:22
  • What would you say is the difference between motorcycle engine and motorcycle's engine? I don't have a distinction in my dialect, unless maybe if I'm a motorcycle mechanic and want to distinguish between the motorcycle engines I possess and the one that happens to be used in the motorcycle I ride. Oct 22 '14 at 18:31
  • "Motorcycle's engine" cannot be used if you only have an engine, and no motorcycle for it. "Motorcycle engine" is any engine designed to work in a motorcycle, even if it has not yet been installed.
    – Amadan
    Oct 23 '14 at 6:56
  • Right, I know that. What I was saying was that I would only use the term "motorcycle engine" unless in rare circumstances. Oct 23 '14 at 23:15

Womens college, women's college, woman's college are all valid, grammatical and used appropriately. Each of them means a different thing. One may of course be more predominent and thus make the rest seem ungrammatical.

Just see use-cases to understand the difference.

  • 3
    Womens college is grammatical? So the plural of women is womens?
    – Robusto
    Oct 22 '14 at 12:37
  • @Robusto :) No, it of course isn't. However, Womens college is not just right but the most common among all. English!
    – Kris
    Oct 22 '14 at 12:41
  • 2
    @Kris, I strongly disagree. Women's college is by far the most common and is the correct form.
    – Jace
    Oct 22 '14 at 13:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.