1. One more; an additional: had another cup of coffee.2. Distinctly different from the first: took another route to town.3. Some other: put it off to another day.
PRONOUN:
1. An additional one: one encore followed by another.2. A different one: This shirt is too big; I'll try another.3. One of an undetermined number or group: for one reason or another. See Usage Note at each other.
ETYMOLOGY:
Middle English on other : on, one; see one + other, other; see other.