Possible Duplicate:
“My another account” vs. “my other account”
Sometime it's vague for me when to use other vs another. For example,
- You need to buy other book
- You need to buy another book.
What's the difference between them, and when to use other or another?
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There's a formula:
another = an + other.
Think of it as of an article plus the word "other" that have historically merged into one word. Grammar requires some article before "other book"; either "the" or "a." Depending on the context, you get either "You need to buy the other book" (if, for instance, the guy bought only the first book out of the set of two) or "You need to buy an_other book" (any other).
Another implies extra or additional with respect to the current amount. "I'm going back for another sandwich."
Other is an adjective implying it is different than the object in discussion. "Pass me my book. Not that one, the other one." It can also be a pronoun referring to things or people: "Let's wait for the others to arrive."
Going back to your example, if I said "You need to buy the other book," I'd be implying a mistake has been made, not that you should buy an additional book as if I had said "You need to buy another book."
English can use definite and indefinite articles before other thing (or other used as a noun) in the same way it uses them before nouns in general; by contrast, Spanish, for example, does not use an indefinite article before otra cosa. But instead of writing an other thing, English writes another thing, losing a space.
So it is "You need to buy another book" in the same way it is "You need to buy a red book" developing from "You need to buy a book", but "You need to read my other book" coming from "You need to read my book".
You can break another apart as in "I'm not a partner or a bit-on-the-side, I'm a significant other".
