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I've always found it a bit peculiar that Apple's marketing refers to iPhone without an article. There is a question here which discusses why it feels more natural to use an article, but I'm wondering what the actual grammatical status of the word "iPhone" would be.
Buy iPhone at your favorite Apple Retail Store.
My initial impression after reading this would be to interpret "iPhone" as its own plural, like "deer".
Now iPhone is even bigger on productivity.
Now it can't be exactly like "deer", as you would expect to see "iPhone are", "the iPhone" or "an iPhone".
So looking at both examples together, my next thought would be that perhaps "iPhone" is a mass noun, like "data". Substituting "data" in either sentence seems acceptable.
...we could have sold many more iPhones...
Now they've made "iPhone" plural. I'm not sure how you could fit "data" into this sentence other than the slightly odd "datums".
The new iPhones include iOS 8...
...and now "iPhone" finally has an article. The only word I can think of that can go in all of these sentences now is "coffee", but I'm not sure this is actually the same. "Coffee" seems to have the odd property that "a coffee" is different from "coffee", "a coffee" always means "some coffee in a vessel", and "coffees" is always the plural of the "a coffee" form even if you omit the article (as in "Coffees are expensive.", which is distinct from "Coffee is expensive.").
So what category does the noun "iPhone" fall under? Is it equivalent to "coffee"? (And if so, what exactly is going on with the different forms of "coffee"?)