the question has already been asked here on our website. You could find the answer here. http://www.italki.com/question/244021

"Another" = "An other" It's just convention to write it as one word. You don't need to memorise a description of what "another" means; you just need to know how to use articles and remember to not write a space when you write "an other".

Also, "I don't want this one. I want the other." = "I don't want this one. I want that one." :)

Say there are two bottles of beer on a table. One is near you and one is near your friend. You could say "I don't want the beer closest to me. I want the other." So "the other" here refers to the beer next to your friend. :) Say there are five beers on a table and you drink one. You can then say "May I have another?" In this case, "another" means "one more". :)

The best way to answer this for me is to give you an example "I'm finished with this beer, could I get another one... actually, I didn't really like this one. What other beers do you have?"