Is there more than one word for 'we'?
I don't think that ειματε exists.
είμαστε (with accent and an additional sigma) means "(we) are". That is, it's the form of "to be" that is specific to the subject "we" (like how "is" in English is specific to the subject "he, she, it" - you can't say "you is" or "they is").
Since verb forms in Greek are all specific to a specific person, you can leave out the pronoun itself. So "we are" could be either εμείς είμαστε (with pronoun) or simply είμαστε (without). You'd usually use the pronoun only for emphasis in such a case, so εμείς είμαστε might be better translated as "we are" (in contrast to someone else who is not).