This document discusses the perfect, pluperfect, and future perfect passive tenses in Latin. These tenses are all formed using the fourth principal part of the verb plus a form of the verb "sum". Specifically, the perfect passive uses the fourth principal part plus the present form of "sum", the pluperfect passive uses the fourth principal part plus the imperfect form of "sum", and the future perfect passive uses the fourth principal part plus the future form of "sum". The fourth principal part must agree with the subject of the verb in case, number, and gender.