Sometimes when writing a sentence I ask myself when to use what. For instance: "the screen of my iphone" sounds as natural to me as "my iphone's screen". Are both okay?

I do know that "the shirt of my girlfriend" is not really correct and that it should be "my girlfriend's shirt", but what are the exact rules?

To me apostrophe s is mostly the safe route when I am in doubt, would you agree?

  • There is an ancient "rule" that once prevented some English speakers from using the Saxon genitive to denote possession by inanimate things, and there are still some who feel that my iPhone's screen "sounds wrong". When it is pointed out that my iPhone's keys does not "sound wrong", they realize that it is the alliteration of s that causes the problem, and not the Saxon genitive. Lesson: avoid the alliterative s when possible. – P. E. Dant Reinstate Monica Jul 27 '17 at 22:50

Normally we reserve the "periphrastic" of form of the possessive to refer to that which is an integral component, not a possession.

The screen of my phone yes

The car of my sister no

The possessive with 's works in both cases.


Using "of" in simple examples "the car of my sister" tends to sound like translationese. In most examples when the noun is simple, you can use the possessive.

However, a noun can be complex. "The tall man I met at work" is a noun phrase, and *"The tall man I met at work's teeshirt" is problematic. It becomes hard to parse such phrases. Using "of": "The teeshirt of the tall man I met at work" is less likely be confusing. There are other ways to express this.

Using "of" allows me to put an article or another determiner with the object being possessed: "He is a friend of Sue" to imply that Sue has many friends. Consider now the word "part". You can say "a part of the sentence", but not "a sentence's part". Again, by using "of" you can place the article with "part".

Sentences with "of" can be more flexible because you can more easily add modifiers, sometimes that is convenient.

Then there are proper nouns with of as part of the name. You say "Bank of Scotland" or "Houses of Westminster", because it is part of the name of these institutions.

No doubt there are other situations in which "of" is preferred.

  • Honestly, now: would you actually say "The teeshirt of the tall man I met at work"? I can hear "on", or even "worn by", but "of"? – P. E. Dant Reinstate Monica Jul 28 '17 at 1:30
  • I'd use a pronoun. "I met this really tall guy at work. But his teeshirt ..." – James K Jul 28 '17 at 5:23

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