0

My own sentences where "that" = "which":
(1a) The forum (that) I posted this question is for English language learners. — (I know it's) incorrect
(1b) The forum (that) I posted this question on is for English language learners. — (I know it's) correct
(1c) The forum which I posted this question is for English language learners. — (I know it's) incorrect
(1d) The forum which I posted this question on is for English language learners. — (I know it's) correct

from wordreference.com:
(2a) It happened the day (that) the car accident took place. — (where it's said that it's) correct
(2b) It happened the day (that) the car accident took place on. — (where it's said that it's) incorrect
from wordreference.com:
(2c) It happened the day which the car accident took place. — (where it's said that it's) incorrect
(2d) It happened the day which the car accident took place on. — (where it's said that it's) correct but less natural than (2a)

That is, the sentences with "which" are subject to the same rules:
(1с) & (2c) are both incorrect,
(1d) & (2d) are both correct.
But why are the sentences with "that" not subject to the same rules?:
(1a) is incorrect whereas (2a) is correct,
(1b) is correct whereas (2b) is incorrect.

It's said on "wordreference.com" that in (2a-d), for some reason, "that" ≠ "which" but "that" = "on which". To me it's a very strange and unclear explanation because I can't see any differences between (1a-d) and (2a-d) in terms of grammar.

Could you explain to me please the rule:
when "that" = "which" and when "that" = "on which"?
Or more generally:
when "that" = "which" and when "that" = "some preposition + which"?

3
  • 1
    I find 2b to be OK, though the "on " at the end is awkward. I would prefer It happened on the day (that) the car accident took place, and for this sentence an extra "on" at the end is definitely wrong.
    – Peter
    Commented Oct 21, 2022 at 0:48
  • Both (1d) and (2d) would be better as "The forum/day on which..." (without the later 'on'). Commented Oct 21, 2022 at 8:56
  • 1
    Related: ell.stackexchange.com/q/233484/21520
    – athlonusm
    Commented Oct 21, 2022 at 15:42

1 Answer 1

-1

(1a) is incorrect because you can't say "I posted the question the forum" - you have to include on, even when the word order is changed.

Sentences about when something happened are a special case. We can say "The day the accident took place" without having to include on which. "The day that the accident took place on" sounds very awkward.

1
  • Note that we can say "It happened that day" or "It happened on that day".
    – Colin Fine
    Commented Oct 21, 2022 at 10:02

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .