So far I thought the words who and that are usually interchangeable:

  1. There is the man who saw me.

  2. There is the man that saw me.

Both sentences seem fine, who can be replaced with that. But in the following examples:

  1. This is the man to whom I spoke.

  2. This is the man to that I spoke.

The #2 sounds odd, which is why I don’t think it might be correct.

The same observation for the words which and that, while

  1. This is the ball which we used today.

  2. This is the ball that we used today.

Seem to be in order and which can be replaced with that. But in the following examples the #2 sounds odd again.

  1. This is the ball with which I scored.

  2. This is the ball with that I scored.

I wonder if there’s any rule regarding the interchangeability of the above mentioned words.

  • I hope you don't mind - I edited your question because the to didn't work with the verb you were using ... I won't be offended it you roll it back. Or you can just fiddle about with a full stop and my name will disappear from your post! Commented Oct 28, 2014 at 20:17
  • @Araucaria, on the contrary: I feel honored and flattered, the post looks far more better. Commented Oct 29, 2014 at 11:20

2 Answers 2


Your observations are pretty precise.

In Standard English (whatever that is), relative that is not used a) to head non-restrictive ('supplementary') relative clauses or b) as the object of an immediately preceding ('pied-piped') preposition. Only wh- forms (who/whom, which) are used in these contexts.

a) That is John, {whom/that} I interviewed yesterday.
b) This is the ball with {which/that} I scored.

However, that may head a clause in which it acts as object of a 'stranded' preposition:

okThis is the ball that I scored with.

In colloquial English rule a) is relaxed, because in improvised speech the distinction between restrictive and non-restrictive clauses is not so strongly marked as it is in composed speech—a restrictive clause often occurs to a speaker 'after the fact', so it is pragmatically non-restrictive even when it is semantically restrictive. But rule b) is almost universally observed in all registers.

marks an expression as unacceptable

  • Well done! Thank you! It’s a real pleasure to read whatever you write. +1 Commented Oct 29, 2014 at 7:11

When we have 'restrictive' or 'integrated' relative clauses we can usually use that instead of which or who(m). We don't usually use that with non-restrictive relative clauses:

  • *Your Dad, that I've known for many years, is a really nice guy. (wrong)

There are some special cases when we can't use that with restrictive relative clauses either. The following sentence is fine:

  • That's the man that you were talking with.

However, if we move the preposition to the front of the relative clause, that cannot be the complement of the preposition. We have to use whom or which as appropriate:

  • That's the man with whom you were talking.
  • *That's the man with that you were talking. (wrong)

[Notice that we cannot use who as the complement of a preposition. We have to use whom:

  • *That's the man with who you were talking. (wrong)

Many writers on this site tell people not to use whom, but this is one situation where you have to!]

Another situation in which it's better not to use that, is after the demonstrative pronoun, 'pointy' that.

  • #Do not do that that you know to be wrong. (awkward)

This is not grammatically wrong, but it's a bit awkward, and it can be difficult to read. Lastly we may want to contrast the difference between a person or thing that might have done something. In this case we may want to say who or which. This cannot work with the word that:

  • Never trust in any people or in any things who, or which, you cannot actually see.
  • *Never trust in any people or in any things who, or that, you cannot actually see. (wrong)

The Original Poster is, therefore, correct: we cannot always use that instead of who(m) or which. The following sentences from the original question are ungrammatical, because that cannot appear as the object of a preposition:

  • *This is the man to that I spoke. (wrong)
  • *This is the ball with that I scored. (wrong)

I hope this helps!

  • Sometimes on ELL we add little footnotes to our posts explaining symbols like * and # because not everyone here is familiar with them.
    – user230
    Commented Oct 28, 2014 at 13:35
  • @snailboat Do you think that's more helpful than doubling up (i.e. putting (wrong) or (awkward) next to the examples)? [Missing (awkward) has been duly added!] I'll basically take your guidance on that .... Commented Oct 28, 2014 at 13:40
  • 1
    Oh, your edit is fine. I figure anything that gets the point across is good :-)
    – user230
    Commented Oct 28, 2014 at 13:44

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