When one wants to list various cases/classes/categories/types of objects in a string of conjunctions, is it preferable (or even mandatory) to keep on using (the same) preposition in front of each one them?

Moreover, does singular or plural form of the word "case", "class", "category" make any difference in the previous question?


  1. In the present article, we study the case of X, of Y and of Z objects.
    (in this example, as in most of the ones I have in mind, it is the preposition "of" which is relevant to my question).

  2. We study the cases/classes of X and of Y objects.
    We study the cases/classes of X and Y objects.

Although it is rather clear that, in the singular case, the absence of "of" in later conjuncts may lead to a logical confusion (e.g., mistakenly taken as the one class/case of objects which are both X and Y), when it comes to plural of the words "case", "class", etc., this might not be an issue. Still, there might anyway be a rule in the plural setting as well.

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    Related: There is in the news at the moment a "former Bishop of Lewes and Gloucester," which should be "of Lewes and of Gloucester" because his title wasn't Lewes and Gloucester (as in "Bath and Wells" or "Ripon and Leeds" or "St Edmundsbury and Ipswich") but first Lewes and then Gloucester afterwards. – Andrew Leach Nov 14 '12 at 15:22
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    How about "In the present article, we study the class of these following objects: X, Y, and Z."? Not that I know anything specific about your class nor objects. – Damkerng T. Nov 14 '12 at 15:28
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    I am particularly interested in the (syntactical) format which is given in the examples (@Damkerng). For my purposes, it is often the case that more than two cases/classes of objects are involved in any given sentence (@Bill). Thus, I would really appreciate a general rule rather than possible restatements or personal choices. – kvagk123 Nov 14 '12 at 15:38
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    In the 1st format ex., the "of" must be in front of all 3 (the case of X, of Y, and of Z objects) or else it's not parallel construction. It's required & considered ungrammatical if it's not there. In the 2nd format ex., it's required to ensure the reader knows X & Y are separate & not a paired singleton like Bath & Wells. I'm sorry my comment sounded like a personal choice. I always label personal choices as such; otherwise, I mean it's normal for American English. OTOH, sometimes users here point out alternative rules. I'm an editor, not the English Academy president. – user21497 Nov 14 '12 at 16:33
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    The case of red, white, and blue balls is ambiguous. Are they all R-W-B, or are some R, some W, some B? The case of red, of white, and of blue balls is grammatical and not ambiguous. The cases of red, of blue, and of white balls is neither ungrammatical nor ambiguous. Style is another issue. There's always another way to express an idea. I'm not judging style here. And it may very depend on what X, Y, & Z are, but we don't know yet, so we can't judge a real sentence until we get one. – user21497 Nov 14 '12 at 21:09

As long as the prepositions before each object are the same, it's both easier to parse and stylistically preferred to not repeat the preposition.

In the present article, we study the case of X, Y and Z objects.

Repeating the of in this example, as you did above, actually decreases my comprehension, as I have to spend a small amount of mental energy to properly construct the coordination.

The only time that I would repeat the preposition is when it differs:

In the present article, we examine the objects from X, for Y, and within Z.


According to William Strunk's Elements of Style (Chapter 3, suggestion 15), "an article or a preposition applying to all the members of a series must either be used only before the first term or else be repeated before each term."

In other words, either approach is acceptable as long as you remain consistent.

I'd say that in general the prepositions should be omitted unless you want to emphasize that the items in the list are separate.


Since you are at liberty to repeat among any prepositions - essentially contriving a series of phrases - or to cluster words or phrases as objects of fewer (repeating and/or non-repeating) prepositions, the only determiner must be what gives clearer meaning to you as the author. Try both/all combinations; use what makes better sense without ambiguity. None are wrong unless they can't be read exclusively right.

Did you see an example in the above paragraph? I could have said or cluster or to cluster. To me, to cluster is more accurate.

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