The string an other is vanishingly rare in English. In contrast another is positively pervasive. I think it would be fair to say that the second has eclipsed the first to the point of making the first unacceptable, even though it is a grammatical string.

Understanding the Context

Both an and another are members of the category of determiners, while other, on the other hand, is an adjective. There's no grammatical ... 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.

Key Insights

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 ... Other (other + plural or uncountable nonspecific noun) You can say: 'If I had another five dollars I could afford it.' - Five dollars is single unit of money. I have to admit that this answer lacked more information previously. With numbers it is acceptable to use another, but there are exceptions. 3 The formal discourse marker used by the OP; "on the one hand ...

Final Thoughts

on the other hand" expresses two contrasting ideas, opinions or facts. In view of this fact, I suggest the following alternatives: Although I like product A, product B also appeals to me strongly. I like product A, although product B is also appealing. Alternatives to the "on the one hand... on the other hand" construct Which of these two sentences would be correct? I recall that he was out looking for something or another.

I recall that he was out looking for something or other. Basically, should I use "something... grammar - Something or other vs something or another? - English ...