# Difference between “an” and “one”

Forgive me if I miss something very obvious; English is not my native language.

I am currently taking an online (sort of) Math class that aims to teach creating/writing unambiguous Mathematical statements. (Don't worry, I'm in the right SE site and my question isn't about Math). The professor gave an example of ambiguity in human language (English) that according to him may mean the same but actually have two different meanings.

He said, "One American dies of melanoma almost every hour." is not the same as "Almost every hour, an American dies of melanoma."

Well for me, the two sentences means the same. Is the article "an" is reason for the supposed change in meaning of the sentence? Or is it the placing of the adverbial phrase "almost every hour"?

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I won't "forgive" you if you ask something obvious (because there's no offense taken, thus no need to forgive). However, I will post a link to the site for English Language Learners, where you might feel more comfortable asking questions like this one. That site was especailly designed for questions like this. Your question here is probably fine, but you might want to consider joining there as well. Many regulars here are very active there as well. – J.R. Mar 19 '13 at 10:04
'One American dies of melanoma almost every hour' -and he's getting quite annoyed about it. – TimLymington Mar 19 '13 at 11:37

This is not English. It is mathematical logic. Your professor is trying to contrast the two statements:

(1) ∀ hour ∃ American who dies of melanoma.
(2) ∃ American who dies of melanoma ∀ hour.

As @Tim's comment suggests, the second statement means that the same American dies of melanoma every hour.

Neither of these statements is what either of the English sentences

(1) Almost every hour, an American dies of melanoma,
(2) One American dies of melanoma almost every hour,

really means in English. They both mean the same thing. If you want to state it mathematically, you need to say something like:

Consider the number of Americans n who die of melanoma between times t1 and t2, where the times are measured in hours. For large t2t1, n is with high probability slightly less than t2t1.

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I understand that you are confused about the uses of A and ONE. Sometimes you can use them interchangeably but sometimes not. A is an indefinite article. You should use it before a singular noun that starts its pronunciation in consonant sound. "A parrot can imitate the human voice." Here you cannot use ONE before parrot because ONE indicates a number while A does not. If you say "One parrot can imitate the human voice", you are referring to only one parrot, not all parrots. At the same time, "A parrot can imitate human voice" means that all parrots or any parrot can imitate human voice. A means any while ONE means only one in number. At the same time, there are occasions when you can use A and ONE interchangeably. When you say "I want a pen" or "I want one pen", both of them are correct. Here you refer to a number. Likewise, you can say "a hundred dollars" or "one hundred dollars". "One" is more formal here. Remember: when you want to stress the number, use ONE; when there is nothing to do with number, use A.

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So which case is OP's situation? – Fr0zenFyr Mar 19 '13 at 10:09

A is used as an indefinite article or determiner. One is used as an indefinite pronoun. Sometimes they are used interchangeably.

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## protected by RegDwigнt♦Nov 8 '13 at 18:46

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