Creating a slide show this morning, a task that demands brevity and therefore frequent recourse to abbreviations, I wrote "TMs" for "trade marks". Autocorrect didn't like it, but that was no surprise and I overrode it. Then I wondered whether the correct way to form the plural of an abbreviation wasn't just to add an "s" - should I be adding another "M" (or "m", perhaps)? After all the plural of "p" for page is "pp", and of "op" for work (opus) is "opp". (The use of full points turns out to be another contentious matter.)
In fact The Economist Pocket Style Book (Economist journalists must have bigger-than-average pockets) tells me that the right way to set out an abbreviation is in small capitals, and to use a lower case "s" for plurals. I suppose that in the name of a case (e.g. "Re Le Mans TM") the phrase would have capital initials by virtue of forming part of the title - "title case" is in fact the correct expression for that, I think. And actually the words of the trade mark should be in upper case: Re LE MANS Trade Mark (BL O-012-05, a decision of Richard Arnold QC as he then was). But of course the heading of the decision is in block capitals, although in the body of the decision it is in upper case. None of the three IP textbooks at my right hand have it in the table of cases, so no guidance from there. I could have scanned them for another such decision but life is too short, especially when I can reach up to the top shelf and take down a dusty copy of the 12th edition of Kerly - in which I look up the Perfection case (Crosfield [1910] 1 Ch. 118; 26 R.P.C. 561) and find the trade mark rendered just like that - a capital initial only.
Neither Fowler's Modern English Usage nor The Oxford Style Manual offer any assistance in their entries on abbreviations. The King's English doesn't even have an entry in its index for the topic. The Oxford Dictionary of English Grammar is however more helpful: it tells me that the initial letters of the (main) words of a phrase should appear in upper case, so BBC and OTT get the same treatment, which is not what The Economist prescribed. It goes on to say that "[t]here are a few special written conventions for plurals", of which it gives three: "pp", which is from where I embarked on this little voyage through English grammar, MSS which I was also thinking about, and "ff" for "following pages". Elsewhere, I read that "p" stands not for "page" but for its Latin equivalent, "pagina", and "pp" ("paginae") is an example of a special rule for Latin words or expressions in English usage. ("Op" and "opp" presumably follow the same rule.)
Finally, since it seems that uppercase or small capitals is correct, and an added "s" rather than a doubled last letter is right, should there be an apostrophe? I can see a reason why there should be a difference in the treatment of contractions (e.g. Dr) and true abbreviations, where there is something missing between the initial letter in the abbreviation and the plural "s". But The Oxford Style Guide says just add the "s", so TMs would be correct, and I could have saved myself half an hour or so on this interesting diversion. Maybe some helpful reader will be able to guide me further, but unless I hear otherwise I'll go with TMs.
In fact The Economist Pocket Style Book (Economist journalists must have bigger-than-average pockets) tells me that the right way to set out an abbreviation is in small capitals, and to use a lower case "s" for plurals. I suppose that in the name of a case (e.g. "Re Le Mans TM") the phrase would have capital initials by virtue of forming part of the title - "title case" is in fact the correct expression for that, I think. And actually the words of the trade mark should be in upper case: Re LE MANS Trade Mark (BL O-012-05, a decision of Richard Arnold QC as he then was). But of course the heading of the decision is in block capitals, although in the body of the decision it is in upper case. None of the three IP textbooks at my right hand have it in the table of cases, so no guidance from there. I could have scanned them for another such decision but life is too short, especially when I can reach up to the top shelf and take down a dusty copy of the 12th edition of Kerly - in which I look up the Perfection case (Crosfield [1910] 1 Ch. 118; 26 R.P.C. 561) and find the trade mark rendered just like that - a capital initial only.
Neither Fowler's Modern English Usage nor The Oxford Style Manual offer any assistance in their entries on abbreviations. The King's English doesn't even have an entry in its index for the topic. The Oxford Dictionary of English Grammar is however more helpful: it tells me that the initial letters of the (main) words of a phrase should appear in upper case, so BBC and OTT get the same treatment, which is not what The Economist prescribed. It goes on to say that "[t]here are a few special written conventions for plurals", of which it gives three: "pp", which is from where I embarked on this little voyage through English grammar, MSS which I was also thinking about, and "ff" for "following pages". Elsewhere, I read that "p" stands not for "page" but for its Latin equivalent, "pagina", and "pp" ("paginae") is an example of a special rule for Latin words or expressions in English usage. ("Op" and "opp" presumably follow the same rule.)
Finally, since it seems that uppercase or small capitals is correct, and an added "s" rather than a doubled last letter is right, should there be an apostrophe? I can see a reason why there should be a difference in the treatment of contractions (e.g. Dr) and true abbreviations, where there is something missing between the initial letter in the abbreviation and the plural "s". But The Oxford Style Guide says just add the "s", so TMs would be correct, and I could have saved myself half an hour or so on this interesting diversion. Maybe some helpful reader will be able to guide me further, but unless I hear otherwise I'll go with TMs.