"the changes that happened" or "the changes happened"

Question

I was arguing with a classmate about whether to use "that" in this phrase or not?

The map shows the changes (that) happened in the area.

Which is correct "the changes that happened" or "the changes happened"?

I think that the sentence is correct with and without "that", but he thinks that it is necessary to use "that".

Answer 1

There are two possible sentences that mean different things:

To say:

The map shows the changes that happened in the area.

is focusing our attention on the changes.

If you break the sentence in two, the parts would read:

The map shows the changes. The changes happened in the area.

To say:

The map shows the changes happened in the area.

omitting that, is focusing our attention on where the changes happened.

To break the sentence in two, the parts would read:

The map shows where the changes happened. They happened in the area.

Thus omitting that gives a completely different emphasis to the sentence.

So you would either include or exclude that depending on what you wanted to say. Grammatically, both are correct.

Answer 2

I agree with your friend. You should use "that" in

The map shows the changes that happened in the area.

Perhaps the map is often updated. In that case you can leave out "that" like

The map shows the changes happening in the area.

Answer 3

This use of "that" is not, strictly speaking, optional.  Dropping it results in a different sentence: 

The map shows [that] the changes happened in this area. 

In the sentence above, the "that" is optional.  Even when it's not included, the entire clause "the changes happened in this area" stands as the object of the verb "shows". 

This happens because clauses* in English require subjects. 

 

The map shows the changes that happened in this area. 

Your original model gives the clause formed by "happened" a suitable subject.  Since "that" can also mark a clause as relative, the entire subordinate clause "that happened in this area" serves as a modifier of the noun "changes". 

 

These two model sentences are quite similar, but not exactly the same.  With the optional "that", the changes themselves are not necessarily shown.

Answer 4

I think the problem is the "the". Here are some alternatives, and how (I believe) they should be interpreted (I've omitted the "in the area" - it doesn't add anything):

1. The map shows changes happened.

   This is almost an exclamation - a discovery:

   • "The map shows changes happened!"

2. The map shows that changes happened.

   This is almost an argument:

   • "Changes didn't happen!"
   • "The map shows that changes happened!"

3. The map shows changes that happened.

   This is almost explanatory - the reason for the map. Note it doesn't (necessarily) show all the changes - see #5 below.

4. The map shows the changes happened.

   This is simply not grammatically correct. This is a definite statement:

   • "The map shows the changes happened!"

5. The map shows the changes that happened.

   This implies that it shows all the changes that happened - or at least, all the changes of interest to the people talking.

6. The map shows that the changes happened.

   Again, this is argumentative, like #2 above. But this time it's talking about specific changes (the "the"):

   • "The changes didn't happen!"
   • "The map shows that the changes happened!"