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Why don't we use " 's "(possessive S) in the first sentence as in the second one?

  1. I have the same color eyes as my father.
  2. My personality is very similar to my father's.

Can we use "my father's" for the first sentence and "my father" for second one?


  1. She was born on the same day as me.
  2. Her ideas are quite similar to mine.

Why in the first sentence do we use object pronoun, but possessive pronoun in the second one.

marked as duplicate by tchrist, phenry, user66974, Rory Alsop, FumbleFingers Jul 14 '14 at 11:34

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  • 1
    "Her ideas are quite similar to mine" means "Her ideas are quite similar to my ideas." But in *"She was born on the same day as mine." My what? – Peter Shor Jul 12 '14 at 18:58
  • Tnx.what about "my father" and "my father's" is it incorrect to use them interchangably in those first two sentences. Because it seems correct to my ear – amirhossein Jul 12 '14 at 19:01
  • 1
    They're interchangeable in (1). People do use (2), but strictly speaking they shouldn't because your personality isn't the same as your father; it's the same as your father's personality. – Peter Shor Jul 12 '14 at 19:03
  • In both of your examples, the meaning of (2) is apparent, so people wouldn't get confused if you left off the possessive. But consider "her daughter is the same size as me" and "her daughter is the same size as mine". They mean different things. – Peter Shor Jul 12 '14 at 19:06
  • So,the second sentence " her daughter is the same size as mine" the same size of my size,but what about first one.how is it different from the second one? – amirhossein Jul 12 '14 at 19:08

The sentences are in a different format. In the first the subject is 'I' & in the second the subject is 'My personality'.

It would also be correct to say a) My eyes are the same colour as my father's. b) I have a similar personality to my father.


To understand what is going on here it helps to undo the ellipsis. Ellipsis is the leaving out of one or more words in the second of two parallel constructions, in the faith that a reader or hearer can and will mentally supply them on the basis of the first.

  1. I have the same color eyes as my father [has].
  2. My personality is very similar to my father’s [personality].

The second pair is a little trickier.

  1. She was born on the same day as me I [was born].
  2. Her ideas are quite similar to mine my [ideas].

For #1 of this second pair, the substitution of me for I (only when the was is left out) is characteristic of colloquial and/or informal usage. Some will prefer and use I there even in the elided form; inverse snobs will despise them for it. For #2, the possessive pronoun my characteristically changes to mine when the word for what is possessed is elided, so when we restore that it reverts to my.

(In earlier versions of English, my also became mine when followed by a vowel sound, much as a becomes an; Julia Ward Howe was being retro in writing “Mine eyes have seen . . . .”)

  • The similar to me/mine and similar to my father/father’s comparison (whether they mean the same thing, different things, or are illegal) reminds me a lot of mistaking one’s wife for a hat. :) For what it’s worth, my is a possessive determiner (even when it is spelt mine eyes) not a pronoun because it cannot be a standalone substantive: you cannot say ∗My are ready — whereas mine is properly a possessive pronoun, since you can say mine are ready. – tchrist Jul 12 '14 at 21:29

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