Many of the postpositions in Finnish originate from inflections of words that are no longer themselves used.
If a postposition requires the genitive case, and a personal pronoun in genitive (minun, sinun, hänen, meidän, teidän, heidän) is used before the main word, the corresponding possessive suffix (-ni, -si, -nsa / -nsä, -mme, -nne) is appended to the postposition in standard Finnish. A first-person or second-person pronoun can then be omitted. Some examples:
Note however that the possessive suffixes are not that common in colloquial Finnish, in which case the genitive pronouns may not be omitted (in general, colloquial Finnish tends to drop pronouns considerably less often than standard Finnish).
The possessive suffix cannot be appended to the shortened postpositions ali, yli, ohi, taa, luo and läpi. Either the corresponding longer form alitse, ylitse, ohitse, taakse, luokse or lävitse is used instead, or the possessive suffix is left out.