I am confused regarding the use of the word "that" when linking phrases together. Specifically, there are many cases where a sentence using the word "that" would sound just fine without the word "that".
"We have data showing THAT these systems are suitable for study"
This sentence would be fine written either way. Is one form correct over another?
A follow up question I would like help on is: what is the difference between "that" and "which"
Thank you very much for your help
When that introduces a clause--a subject and a verb--, it functions like a conjunctions, and so it's optional (...):Originally Posted by Unregistered
The data shows (that) these systems are suitable.
'these systems are suitable' is a clause. Other examples,
EX: This is the book (that) I want.
'I want' is a clause.
EX: They rented the house (that) we used to own.
'We used to own' is a clause.
that introduced required information:A follow up question I would like help on is: what is the difference between "that" and "which".
EX: A suitcase that has no handles is useless.
If we omit the underlined portion above, the result is strange:
EX: ?A suitcase is useless.
which introduced added information--information that's not required, but added for flavour, and since the information it adds is not necessary, commas are used, like this,
EX: The UFO, which I saw, was round. ~ The UFO was round.
The above sentence expresses two things: 1) The UFO was round, and 2) by the way, I saw it.
The fact that I was the one to see the UFO is not all that important to me or to the meaning I want to express, so I added it in using 'which'. If it were important to me or to the meaning I want to express then I would use 'that',
EX: The UFO that I saw was round.
The above sentence expresses one thing: 1) I saw a round UFO.
Since 'that' in the example above introduces a clause (i.e., I saw) it's optional:
EX: The UFO (that) I saw was round.