Double Letter S in American English
Both Ss Pronouned as the sound of Z with the following syllable
brassiere dessert possess
Both Ss Pronouned as the sound of SH with the preceding syllable
aggression compression degression depression digression impression passion secession
Both Ss Pronouned as one S with the preceding syllable
assay asses asset assignation bassinet bioassay brasserie brassy casserole cassowary
chassis classic classify espresso hassle impressive incessant massacre molasses passable
passage passel passenger passive potassium pressurize professor progressive suppressive  
Both Ss Pronouned as one S with the following syllable
assail assassin assault assemble assent assert assess
assiduous assign assimilate assist associate cassette dressage
fricassee masseur necessary passé passivity