My daughter's English text book has a note which reads if you are directly talking to a person about the only person in your house, it can be capitalized.

For example:

"Mommy, have you seen my tab?"
"What would I do with it? Ask your Sister. She's fond of playing on it"

I want to confirm the capitalization of 'sister' here. This is new to me, actually!

And yes, it has nothing to do with emphasizing 'sister' that many may think the reason of capitalizing. Say--

"Yes, last night I asked Mommy about it, but then she gave a reluctant smile!"

  • 1
    That's a new one on me. The only time I've seen Sister capitalised like that was when the book in question features nuns. Also, what's a tab? At least in Australia, saying somebody has 'a tab' means they have a tablet - usually of Ecstasy. Sister probably should avoid playing on that. :P
    – Damien H
    Aug 7, 2015 at 5:31
  • 1
    Hey, is in AuE 'new on me' common? I think, it's either 'new to me' or 'for me'. And, in India, tab stands for a tablet computer.
    – Rucheer M
    Aug 7, 2015 at 5:35
  • @RuchirM "That's/it's a new one on me" is fairly common down here, yes.
    – Damien H
    Aug 7, 2015 at 6:07
  • 1
    @DamienH a tab is generally a tablet, with a touchpad etc... like a big smartphone but which can't phone... :)
    – Random
    Aug 7, 2015 at 7:17
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2 Answers 2


Your daughter's textbook is not quite accurate.

You capitalize such nouns when they act as names, as the ordinary form of address. "Mommy" is used that way in your second example.

But in your first example, sister is not a name, as its use with a determiner makes clear: it is a common noun denoting a relationship.

If the determiner is omitted, however, the noun is treated as a name, and it is proper to capitalize:

Ask Sister. She's fond of playing on it.

That sort of use of sister is rare, although not unknown; as Damien H says, Sister, capitalized, is usually the title (of reference and address) for a Catholic nun.

  • the sentence is not from the textbook...as I don't remember the exact exercise under the chapter, I just made my own sentence. But what I am curious about is 'noun' of family members taking 'capital'. So, looking at this answer, it seems correct.
    – Maulik V
    Aug 7, 2015 at 7:53
  • And occasionally "Sister", used as a name, gets turned into a nickname, usually "Sissy". (It's still capitalized that way, as you'd expect.) Dec 5, 2015 at 15:56

From the book 'Painless Grammar' by Rebecca, PhD

Capitalize 'mom' and 'dad' when you are calling your parent's name but not when you refer to 'my mom' and 'my dad'.


Hi Mom! Welcome home, Dad


My father and my mother are busy. Could your mom or dad drive us to the movie?

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