As a technical editor, I often come across instances where that and which are used incorrectly to introduce a clause (i.e., a group of words containing a verb that form part of a sentence). Here’s some basic advice for deciding which word is the correct choice.
When used to introduce clauses that provide additional information in a sentence, both words function in a similar manner. The difference is whether the information is restrictive or non-restrictive. But what does that mean?
Restrictive and Non-restrictive Clauses
Restrictive clauses provide information that is vital to the meaning of the sentence or is needed in order for a sentence to make sense. When a restrictive clause is being introduced, the correct word to use is that and no preceding comma is needed.
For example, in the following sentence, the highlighted information is vital to the overall meaning of the sentence.
In the web app, you can open a drawing file that has been saved on the cloud either in your Autodesk drive or any other supported cloud storage provider.
While “In the web app, you can open a drawing file.” can stand alone as a complete sentence, the highlighted information is key to understanding what type of file can be opened from the web app – one that has been saved on the cloud.
Non-restrictive clauses are not required – the sentence will still make sense without them. When a non-restrictive clause is being introduced, the correct word to use is which with a preceding comma. In the following example, the highlighted clause can be removed without affecting the meaning of the main sentence.
Click on the Learning button to display the Learning pane, which contains videos, tips, and online resources.
In this example, the highlighted clause is providing additional information about the Learning pane. Without it, “Click on the Learning button to display the Learning pane.” is still a complete thought and conveys the required information, so the additional clause is non-restrictive.
That Which Affects Your Meaning
There are instances when choosing one word over the other can change the meaning of your sentence. Consider the following two examples:
The Far Clipping and Far Clip Offset parameters, which are set up in Properties, impact how depth cueing works.
The Far Clipping and Far Clip Offset parameters that are set up in Properties impact how depth cueing works.
In the first example, “which are set up in Properties” is used as a non-restrictive clause and indicates that these parameters only exist in Properties. In this case, the clause is pointing the reader to the location of the parameters, but this information is not vital to the meaning of the sentence.
In the second example, “that are set up in Properties” is used as a restrictive clause, which could indicate that there are Far Clipping and Far Clip Offset parameters that exist elsewhere and we are only talking about the ones set up in Properties. If that were true, using the second version of the sentence would be vital to convey the meaning of the sentence.
In this case, there is only one location for these parameters. While most users will know this and are unlikely to confuse the meaning of the sentence in either version, using the non-restrictive version with which takes away any possibility for misunderstanding. At the end of the day, there are a lot of situations where your reader will still understand even if you choose the incorrect word, but in some cases, this distinction between using that and which is essential so that your intended meaning is completely clear.
That Sums It Up
So, if removing the clause would change the meaning of your sentence, use that (without a preceding comma). If removing the clause doesn’t change the meaning of your sentence, use which (with a preceding comma). This will help you ensure that you are always conveying exactly what you are intending to say.
(Note: The information detailed here is following North American conventions. If you’re following British conventions, the rules may be different!)
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