We can use other as a pronoun. As a pronoun, other has a plural form, others: We have to solve this problem, more than any other, today. I’ll attach two photos to this email and I’ll send others tomorrow.

Others is only used as a pronoun. But 'other' has different grammatical functions. On the other hand, 'others' refers to more than one; while 'other' refers to only one thing. As a determiner, 'other' is used before uncountable and plural countable nouns.

Others replaces “other ones” or "other + plural noun". Only others can be used as a pronoun and not other. I don’t like these postcards. Let’s ask for others. (others = other postcards) Some of the presidents arrived on Monday. Others arrived the following day.

We can use another as a pronoun, i.e. not followed by a noun. I’ve already had one beer, but I’ll have another. Others is always a pronoun, i.e. never followed by a noun. I don’t want to use these glasses. Aren’t there any others? (=other glasses) We normally use other + a plural noun.

Other, the other and another can be pronouns. They have the same meanings as before: 'alternative' or 'additional'. In addition, when other is a pronoun it can be made plural: others. I've found a sock. But where is the other? I've got a sock. Do you have one other?