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What is the correct way to pluralize a proper noun like "Raspberry Pi" (a type of small, inexpensive computer)?

Would you say:

  • This project uses two Raspberry Pis
  • This project uses two Raspberry Pi's
  • This project uses two “Raspberry Pi”s

None of the options look right to me. I think the combination of being a proper noun and an unusual second word makes this tricky.

Nathan Long
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    "Raspberries Pi"? – MT_Head Jan 30 '13 at 00:34
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    Related (if not duplicate): What is the plural form of “iPad 2”? – Callithumpian Jan 30 '13 at 00:40
  • Stickler note: single digits are written as words in prose, unless those are part of the brand name etc. (thus “two of iLunch 2”). – theUg Jan 30 '13 at 02:32
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    @theUg - You shouldn't have to apologize for being a stickler on a website dedicated to English Language & Usage. I fixed it. :) – Nathan Long Jan 30 '13 at 03:07
  • @Callithumpian - Interesting. Taking Apple's approach, we'd always say "two Raspberry Pi computers." It does solve the pluralization problem, but seems a bit awkward. – Nathan Long Jan 30 '13 at 03:09
  • Surely uses two Raspberry Pi computers would suffice? – Kyudos Jan 30 '13 at 03:20
  • @NathanLong how to you claim that as Apple's approach, I find much more iPhones than "iPhone phones" and much more "Apple Macs" than "Apple Mac computers", restricting the search to their site. Many of the latter in each is as part of "non-iPhone phones" and "non-Apple Mac computers" respectively. – Jon Hanna Jan 30 '13 at 09:51
  • Good detective work. – Edwin Ashworth Jan 30 '13 at 15:41
  • @JonHanna - it may not be the approach they use, but it's prescribed in http://www.apple.com/legal/trademark/guidelinesfor3rdparties.html – Nathan Long Jan 31 '13 at 01:48
  • @NathanLong they don't even come remotely close to using that themselves. In any case though, they are claiming as the coiners that they use the words as adjectives, and the Raspberry Pi Foundation are not, so even if they followed their own rules, it wouldn't apply. – Jon Hanna Jan 31 '13 at 02:14
  • Obviously, "Raspberry 2*Pi". – Hot Licks Dec 02 '16 at 20:34
  • I don't have enough reputation to comment on posts but I would like to wax about why it isn't "Raspberries Pi" from a programming language angle. 'Court Martial' is a subclass of 'Court'. //If it weren't martial, it'd still be a court. 'Attorney General' is a subclass of 'Attorney'. //If so-and-so weren't the attorney general, they'd still be an attorney. 'Raspberry Pi' or for that matter 'raspberry pie' is not a subclass of raspberry. There's going to be some more nuance involved, I just wanted to say that piece. – Steps Feb 24 '17 at 13:36

3 Answers3

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We can approach this analytically, by authority, or by observation.

Analytically

Okay, to start with our components are at least straightforward; they're both countable nouns, and the plural of raspberry is raspberries and the plural of pi is pis. We'll be using them later.

It's formed from English nouns, so there are four possible ways to treat it.

We could just not think about it, and treat it opaquely, as if Raspberry Pi were a single word. That gives us a plural of Raspberry Pis.

We could treat it as a noun adjunct, where the first noun acts as an adjective. That gives us Raspberry Pis (c.f. coffee shops).

We could threat it as a headless noun, though that seems unlikely to be correct. Anyway, this would give us Raspberry Pis.

We could treat it like a compound starting with the head, which would give us Raspberries Pi, but we'd need some strong reason to favour the first word in this manner. We can rule this out.

Of the acceptable options, since it's a pun on "Raspberry Pie", we'd favour the noun-adjunct case, but they all have the same result.

Likewise, that gives us an etymological approach: It was named to deliberately be similar to "Raspberry Pie" so we should pluralise similarly to "Raspberry Pies". That gives us Raspberry Pis.

By Authority

It was named by, and is a trademark of, The Raspberry Pi Foundation. They use the plural Raspberry Pis.

By Observation

They've been called Raspberry Pis in a variety of places.

Hence, they're Raspberry Pis.

Lynn
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Jon Hanna
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    Unfortunately, that form brings Manneken Pis to mind. – tchrist Jan 30 '13 at 03:13
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    Personally I like "Raspberry Pies". Incidentally, a cluster of Raspberry Pis is known as a "Bramble" – mgb Jan 30 '13 at 03:53
  • Well, it certainly does now @tchrist. – terdon Jan 30 '13 at 04:26
  • +1 but by observation it's not hard to find Raspberry Pi's (more than Raspberry Pis), Raspberry Pies and Raspberries Pi. – Hugo Jan 30 '13 at 06:31
  • @Hugo I found Raspberry Pis more than Raspberry Pi's, though trying to discount repetitions and noting where I looked for one and not the other, is tricky if you're not prepared to do a detailed recorded survey (I'm not). The only "Raspberry Pies" I found in the context of Raspberry Pis seemed to be intended as a joke. – Jon Hanna Jan 30 '13 at 09:52
  • Not happy with 'pi [is a] countable noun'. I'd argue that one homograph of pi (ie the number) is uncount (!!!), like 'root 2'. The Greek letter itself probably needs a Greek font, and the jumbled type word pluralises as pis or pies. – Edwin Ashworth Jan 30 '13 at 15:38
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    +1 for the thoroughness of the answer and the clarity of the conclusion. – TecBrat Apr 19 '13 at 12:44
  • In grammar, one of the widely-accepted use of hyphens is to join prefixes or suffixes when direct concatenation would yield ambiguous or odd results, such as "re-cover" (to cover again). Unfortunately, the hyphen is only usable in cases where the prefix or suffix should be its own syllable. The apostrophe has been adopted for use in one situation where a suffix needs to be part of the preceding syllable--forming the plurals of letters; it's too bad grammarians aren't willing to generalize such usage, since it would seem apropos with product names in a field where... – supercat Aug 05 '14 at 20:06
  • ...many names have semantically-significant trailing s's . – supercat Aug 05 '14 at 20:08
  • @supercat if anything that's become less acceptable than before, as there are several cases where 's was used for plurals that are now either completely dead or well on their way out. – Jon Hanna Aug 06 '14 at 09:36
  • @JonHanna: I know, and I find it somewhat ironic. I think what's happened is that some entities (e.g. the Associated Press) want to have all of their writers use a perfectly homogenous style, and other people get the notion that anything else is "incorrect". Something similar has happened with sentence spacing. Prior to the invention of the Linotype, type would be set with more space between sentences than between words; people using typewriters imitated that practice. Linotypes had trouble with such spacing, however, and because mixing spacing styles would be ugly, some... – supercat Aug 06 '14 at 15:27
  • ...publishers simply standardized on using a uniform-sized space in all cases--a convention which a few decades ago would have been seen as a mark of poor-quality typography. I still think that in cases which require all-caps (e.g. movable-letter signage) apostrophes are appropriate in many cases where they otherwise wouldn't be; while "CDs" may be as readable as "CD's" I would regard "CD'S" as much readable than "CDS". – supercat Aug 06 '14 at 15:31
  • By authority it is. Same reason that GIF has a soft ‘g’. If someone names something, then who is anybody to tell them otherwise? A name is a creation and therefore not something that can be “correct”. As such, it can be whatever the creator chooses no matter how much others may or may not like it. (This is why names do not have translations in other languages. Someone named Pete is Pete in all languages, not Peter, not Pierre, not Piotr, nor Pedro, Petrus, or anything else.) – Synetech Jan 12 '15 at 22:11
  • @Synetech I don't buy any one of my own arguments above, including authority. I do though buy the coincidence of them all. – Jon Hanna Jan 12 '15 at 22:35
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As a trademark, it should be an adjective, not a noun.

This project uses two Raspberry Pi devices.

Edit: The rule that a trademark should always be an adjective comes from the International Trademark Association:

NEVER use a trademark as a noun. Always use a trademark as an adjective modifying a noun.

EXAMPLES:

  • LEGO toy blocks
  • AMSTEL beer

In the past, I have worked for large companies for whom trademarks were important, and this is one of the rules they hammered into us.

Community
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Aric TenEyck
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    Trademark or no, even the creators use it as a noun (e.g. "The Raspberry Pi...") I don't know of any reason to restrict it as an adjective. – Lynn Jan 30 '13 at 05:38
  • As a trademark it can be any part of language at all, but is more likely to be a noun than anything else. I wouldn't even read the use above as an adjective, but as a noun adjunct. Are you saying that "a Raspberry Pi", "an iPhone", "some Jell-O", "a Big Mac", "an aspirin", "an escalator", "a zipper", "some kerosene", "an apple mac" are all wrong? – Jon Hanna Jan 30 '13 at 09:11
  • See my edit above. – Aric TenEyck Jan 30 '13 at 14:12
  • @AricTenEyck- Interesting. Clearly you have cited a valid source, and thus I have removed by downvote. But I would point out this post which I think outlines the instances where that advice is unduly prescriptive and in contradiction with how actual companies use their own trademarks. So take it with a grain of salt. – Lynn Feb 02 '13 at 22:46
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English already has a way to handle compound plurals like this.

Court Martial - singular
Courts Martial - plural

Attorney General - singular
Attorneys General - plural

So I would say

Raspberry Pi - singular
Raspberries Pi - plural

Simples :-)

Robert Baskerville
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    Is "Raspberry Pi" really a compound word with "Raspberry" as its head? It seems to me to be a single word that can't be split. If we did try to split it, it seems to be based on "Raspberry Pie", where the head is the second word "Pie". – herisson Dec 02 '16 at 19:15
  • The more normal way to decide acceptability with a proper name is to follow what the relevant authority (here, the company) do. If they use the plural 'RR Pudz', that's the official way. They are not bound by normal English patterning. – Edwin Ashworth Dec 02 '16 at 19:29