From Wikipedia:

Alkyl groups can also be removed in a process known as dealkylation.

What if we use the instead of a? Will that be a mistake here?

I did an Ngram search and the result is curious:

enter image description here

  • 3
    I would guess there are many processes that remove alkyl groups, and dealkylation is one of them. As one of many processes, I would use a. On the other hand, "the dealkylation process" would be correct. – user3169 Apr 24 '16 at 21:12
  • 1
    It's a reduced relative clause ([which is] known as). Using 'the' and 'a' depends on whether you provided some information already or not. In your case, since you used 'also' I get the impression that you're introducing this process, then using 'in a process' is correct I think. – Yuri Apr 29 '16 at 10:33

I wouldn't say that this is a matter of correctness; it's a matter of how the sentence comes across. Consider these two sentences:

Alkyl groups can also be removed in a process known as dealkylation.

Alkyl groups can also be removed in the process known as dealkylation.

The first one subtly implies that the reader is less familiar with dealkylation; if you say a process, you are introducing dealkylation as something new to the reader. However, when you say the process, you are—again, very subtly—assuming that the reader has heard of dealkylation.

These differences are very subtle—they might be so subtle that I'm seeing something that doesn't really exist. Therefore, I'd like to warn you that, while I'd guess that these sentences would come across in a similar way to everyone, my interpretation may not reflect that of readers at large.


Both forms are in common use and so are, to most people, semantically interchangeable in an example like this.

Whether or not it is strictly grammatically correct may require the skills of a chemist or a deeper understanding of the context.

What form of article we use depends on the nature of the noun. Where it is specific we use the definite article, otherwise we use the indefinite article.

However, there are cases we can use the indefinite article in relation to a specific item

Please pass me a red pen


Please pass me the red pen

Are both acceptable in a context where there may only be one red pen available, but the use of the definite article would lead to ambiguity if there were more.

So the question is, in the context of the source document is dealkylation a specific process or is it used in a more general way?

Am I typing this attempt at an answer sitting at a computer or at the computer? It all comes down to the context.


Using the in place if a would not necessarily be a mistake since both sentences would be understood.

However the thing to keep in mind is that dealkylation is a generic term for a potentially specific process, for example there is O-dealkylation and


Alkyl groups can also be removed in a process known as dealkylation.

refers the generic usage of the term "dealkylation"

Alkyl groups can also be removed in amines using the process known as O-dealkylation.

would refer to the specific process of "O-dealkylation".


The meaning is perfectly clear either way, but here's one more attempt at an answer:

In general, indefinite articles ("a"/"an") imply that there are more than one of whatever you're referring to, and that what you're referring to is any single instance of a larger class. Definite articles ("the") imply that you are referring to one thing very specifically, and which thing it is you're referring to must be either specified or understood by context."

Alright, Mike, flip the switch!

Mike must already know which switch to flip, or ask for clarification.

Alright, Mike, flip a switch!
Tina, would you pass me a pen?

Grammatically, Mike could flip any switch (though for safety, he should verify this is what was intended e.g. via context, such as if the speaker is then supposed to guess which switch was flipped), and Tina could pass any pen, to satisfy the requests.

Alkyl groups can also be removed in a process known as dealkylation.

This example implies that there are multiple different processes which are together in a set sharing the name "dealkylation," and any such process can remove alkyl groups. I think that's correct and what the sentence is trying to say, and even deconstructing the word "dealkylation" I wind up guessing that means "a process that removes alkyls." It admits the possibility that there might be tradeoffs between the various processes: one costs more but works faster, another requires a rare catalyst, another only works on certain types of alkyl groups but not others, additional options perform better at different temperatures, etc., but any of them can remove alkyl groups.

In contrast, using the implies that there is only one process known as dealkylation relevant for consideration in the context of this sentence.

Bookmarks can be purchased at a store that sells books.

This implies you can probably purchase bookmarks at any bookstore and that many bookstores exist within the relevant realm of consideration.

Bookmarks can be purchased at the store that sells books.

This implies there's only one bookstore worth considering (and which one that is should be implied by context, unless the speaker wishes to imply that only one bookstore exists).

Here's another example pair to parallel yours:

Big Macs can be purchased at a restaurant known as McDonald's.

(implied: there are a lot of restaurants known as McDonald's and you can buy a Big Mac at any of multiple locations).

Quadruple Bypass Burgers can be purchased at the restaurant known as Heart Attack Grill.

(implied: there is only one Heart Attack Grill.)

Does that help?


I maybe wrong, but the reason behind choosing 'a' instead of 'the' could lie in the word 'also'.

Alkyl groups can be removed in the process known as dealkylation.

This sounds perfectly acceptable. Having said that,

Alkyl groups can also be removed in the process known as dealkylation.

isn't structurally or grammatically incorrect. But, let us focus on the word 'also'. 'Also' means 'In addition to..', which means it shows the existence of more than one possible events. It sounds better if we use 'a' to pick one among many, rather than using 'the', which depicts exclusiveness.

Note: I have no resources to back my answer, but this is just a suggestion to why using 'a' sounds better than 'the'.

  • I'm not sure you're correct, but thank you for the effort, Varun! – CowperKettle Apr 26 '16 at 14:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.