I am pretty sure that we say "Isn't the X who they think he is", but I also think I have heard "Isn't the X that they think he is" before, but I would choose the former? Is it idiomatic, because I haven't really found an example on Google.

For example:

She isn't the genius who you think she is.

  • With human heads, you can use either "who" or "that".
    – BillJ
    Apr 14, 2019 at 5:39
  • 1
    not clear what you mean about "human heads"?
    – Lorel C.
    Apr 14, 2019 at 5:44
  • I think it means "people".
    – Khan
    Apr 14, 2019 at 5:58
  • @LorelC. Where the head of the noun phrase is a person.
    – BillJ
    Apr 14, 2019 at 6:47

2 Answers 2


She isn't the genius who you think she is.


She isn't the genius you think she is.

means that she isn't as much of a genius as the person addressed (you) believes. It is a way of criticizing the impression that someone has.

He's not the man you think he is.

says that the man is giving a false impression of himself, or at least that the impression "you" has formed is wrong. Normally the implication is that the truth is not as good as the false impression, although it could be used to indicate that the person addressed has significantly underestimated the person under discussion.

Most often I have encountered this form without either "who" or "that". If I were to insert either, it would more often be "that", but it might depend on what term is used in place of "man" or "genius". If the term is one that could apply to a thing as well as a person, i might choose "who" to emphasize that it is a person. But most often I wouldn't include either.

  • I don't know if this is a dialect thing, but I would fine the use of who in your first example entirely unnatural.
    – SamBC
    Apr 15, 2019 at 11:44

I wouldn't use any preposition there, personally.

She isn't the genius you think she is.

However, I would find it okay to use that:

She isn't the genius that you think she is.

These both give the meaning that the speaker believes that the person they are addressing thinks that she is a genius, and the speaker disagrees.

This might be a dialect variation thing (I'm a native speaker of British English), but I would not use who in this context. In other, slightly different contexts, I would use who or that happily, and would say it was 'wrong' to have neither, though I know some dialects would be fine with neither. For example:

I'm the one who called you here.
I'm the one that called you here.

If you just want to say that someone has the wrong impression of someone, you can say:

She's not the woman you think she is.
She's not the woman that you think she is.

That isn't calling out a specific characteristic, just the overall impression. You can also have the same effect with:

She's not who you think she is.

That one can also be used to refer to actual mistaken identity.

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