My question is about the ownership s. It's, is there any clear rule about when we should add the ownership s to words please?

  • more description required.
    – Maulik V
    Commented Jun 27, 2014 at 6:35
  • AFAIK, there is one s in English language named the ownership s, for example, Bank's centeralized computer. I'm talking about that. Commented Jun 27, 2014 at 7:44
  • Whenever we are talking about something that 'belongs' to something else. In your eg, the 'centeralized computer' belongs to the Bank so it gets 'the ownership s'. Is your concern the s or the associated apostrophe?
    – mcalex
    Commented Jun 27, 2014 at 8:08
  • I don't get my question... Commented Jun 27, 2014 at 22:04

1 Answer 1


Do you mean the possessive form of words? The general rule is to add 's to the end of a word. A few notes:

  • However, only an apostrophe is added to words that end with s: James' book, the girls' class.

    • Just to explicitly state, the criterion here is the ending s, not whether or not a word is in plural. 's must be added to plurals that do not end with s: e.g. the children's choir.

    • Add 's as well for words which are pronounced with a /s/ (or /z/) sound at the end but whose spelling don't end in s: such as the mice's hideout. In such cases, it might be better to avoid the possessive form, compare Illinois' surface vs. the surface of Illinois; the first option sounds a little awkward.

  • The possessive form of pronouns do not have an apostrophe: yours, his, hers, its, ours, theirs. Do not the form of its vs. it's: It's interesting how the bird feeds its offspring.

If you're unsure whether to use the possessive form at all, see this short answer (Student's Book vs. Student Book).

Something that may surprise English language learners is that if you are going to somebody's house, you have to use the possessive form as well, e.g. I'm going to my friend's, she's going to Bobby's.

Another heads up, note that some plurals do have an apostrophe, particularly acronyms and letters (for instance: this text only has two K's in it).

  • 1
    "girls's" is never correct; plurals ending in "s" just get an apostrophe after the plural "s", hence: "girls'". Commented Jun 27, 2014 at 15:23
  • Here’s a link for Steve’s comment: Possessive Apostrophe on Wikipedia. You may also wish to add this from that article: “The complete list of those [possessive personal pronouns serving as either noun equivalents or adjective equivalents] ending in the letter [es]s or the corresponding sound /s/ or /z/ but not taking an apostrophe is ours, yours, his, hers, its, theirs, and whose.” Commented Jun 27, 2014 at 16:32
  • @SteveMelnikoff Thanks to both of you (including Tyler)! I've made some changes to reflect your comments and hope the answer is better now.
    – ljacqu
    Commented Jun 27, 2014 at 22:00
  • @ljacqu: Thank you. I gave (+1) vote because the link This short answer was useful. But I'm still waiting for receive more explanation to completely get that issue. Commented Jun 28, 2014 at 6:35

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