DBA update

After a break of several weeks which was due to my supervisor travelling frequently, I finally received his comments regarding the version of the thesis from May. As opposed to previous responses, this time he has left comments in the Word file - topics that need to be written about, expanded upon or explained - but has also edited the actual text here and there. Most of these corrections turn a 'which' into a 'that'.

For example, one of the aims of the research is To discover whether there are similar enhancements which are implemented independently by several companies, thus becoming candidates for inclusion as standard modules. The 'which' has been turned into a 'that'.

I have always thought that my written English is good (even if now and then I get stumped for a word), so these frequent corrections surprised me. I decided to find out when 'that' should be used and when one can use 'which'.

From an English grammar site, I found the following:

That vs. Which: What's the Difference?

Here's an easy way to remember the difference between that and which: if removing the words that follow would change the meaning of the sentence, use "that." Otherwise, "which" is fine. Some people will argue that the rules are more complex and flexible than this, but I like to make things as simple as possible, so I say that you use that before a restrictive clause and which before everything else.

So, with regard to the research aim, removing the clause 'which are implemented independently' would definitely change the meaning of the sentence, and so 'which' should be 'that'. There should be very few superfluous subordinate clauses in the thesis (every word and sentence counts, so there's little room for extraneous content), so every 'which' should be a 'that'.

I haven't looked at most of the supervisor's comments yet, but I imagine that there is much more than my grammar that needs improving (as usual, I initially typed 'which needs improving' before I remembered the above lesson).