Forms of Other

Forms of other are used as either adjectives or pronouns:

SINGULAR: another book
                     (is)
                     another is

PLURAL: other books
                 (are)
                 others (are)


SINGULAR: the other book
                      (is)
                      the other (is)


PLURAL: the other books
                 (are)
                  the others (are)


Note that a final -s is used only for a plural pronoun (others). Another means one more in addition to the one(s) already mentioned. Other/others (without the) refer to several more in addition to the one(s) already mentioned. The other(s) has a different meaning (all that remains from a given number or specific group):


–I have three apartments. Two are mine. The other is yours.