As their names suggest, prepositions go before the substantive phrase they modify, while postpositions follow the substantive phrase. Mostly these are independent words, but there are a few examples which are affixed to the noun in the substantive phrase. The following is a list of the most common pre- and postpositions, with the cases they govern listing in brackets.
Hra'nuan'urrnenir Prepositions
according to - mh'hoaer nnea (+G);
after (temporal) - aihkh (+NA);
after (local) - rheh (+Gen);
against - nelle (+D); thaihnhas (+D);
around - hraefva (+D);
(to) around - hraefva (+NA);
about - sevihf (+D);
(to) about - sevihf (+NA);
as far as - ru (+NA);
at - hrrau, h'rau (+Dat);
(to) at - hrrau, h'rau (+NA);
away from - uaenn (+Gen);
because of - kivoi (+Gen);
before - hra'nuar (+Dat);
(to) before - hra'nuar (+NA);
below - ihfvi (+D);
(to) below - ihfvi (+NA);
between - aethl (+D);
(to) between - aethl (+NA);
by - mh'- (prefix; +G);
down - iut'fehill (+NA);
during - fv'r'astev (+G);
far from - irha (+G);
for (for sy, e.g.) - ssiun (+D);
for (to, towards) - ssiun (+NA);
for (time for a change, e.g.) - vr'- (+Dat, prefixed to modified word);
from - mh'- (+Gen, prefixed to modified word);
in front (of) - hra'nuar (+D);
(to) in front (of) - hra'nuar (+NA);
in - hrrau, h'rau (+Dat);
inside - hrrafv (+Dat);
(to) inside - hrrafv (+NA);
instead of - hrrauta (+G);
into - hrao, hrrafv (+NA);
lead by, under command of - hir'- (+Gen, prefixed to modified word);
near - aedt (+Dat);
(to) near - aedt (+NA);
next to - hhaeh-ahi (+Dat);
(to) next to - hhaeh-ahi (+NA);
of (eg. made of) - nnea (+Gen);
on - hrrau, h'rau (+Dat);
onto - hrrau, h'rau (+NA);
out - nnu (+NA);
out of - mhirrafv (+Gen);
outside - mhirrafv (+Dat);
(to) outside - mhirrafv (+NA);
over - fvi (+Dat);
(to) over - fvi (+NA);
past - siur (+Gen);
regarding - haje (+Gen);
to - i (+NA);
to (until, as far as) - ru (+NA);
to, towards - ssiun (+NA);
to (with a specific thing/person receiving the action) - ih (+Dat);
under - ihfvi (+Dat);
(to) under - ihfvi (+NA);
until (a place) - ru (+NA);
with - sa'- (+Gen, prefixed to modified word);
without - lli (+Gen).
Rheh'urrnenir Postpositions
atop, on top, upon - mibh (+Dat);
(to) atop, (to) on top, (to) upon - mibh (+NA);
from - -hel, -el (+Gen, suffixed to modified noun after case marker if present);
in (temporal, e.g. in 5 hours) - dha (+NA);
through - hsah (+NA);
until, up to (a time) - iut (+Gen);