一か八か[ichikabachika] sink or swim
嘘っ八[usoppachi] downright lie
嘘っ八百[usoppappyaku] full of lies
嘘八百[usohappyaku] full of lies
八釜しい[kamabisushii] noisy

口八丁[kuchihacchou] voluble
三十八度線[sanjuuhachidosen] the Thirty-eighth Parallel
四苦八苦[shikuhakku] being in dire distress
四通八達[shitsuuhattatsu] traffic network extending in all directions
四方八方[shihouhappou] in all directions

黄道十二宮[koudoujuunikyuu] twelve signs of the zodiac
丸十[marujuu] cross in a circle
五十音[gojuuon] the Japanese syllabary
五十音順[gojuuonjun] the syllabary order
五十三次[gojuusantsugi] the 53 Toukaidou stages

五十年祭[gojuunensai] jubilee
五十歩百歩[gojuppohyappo] six of one and a half dozen of the other
五十路[isoji] age fifty
三十戸[sanjikko] thirty houses
三十三所[sanjuusansho] any of a number of sets of thirty-three holy places enshrining Avalokitesvara (esp. those comprising a popular pilgrimage in the Kinki region)

医界[ikai] medical world
医学界[igakukai] medical world
黄金世界[ougonsekai] utopia
下界[gekai] this world
花柳界[karyuukai] red-light district

界隈[kaiwai] neighborhood
界面[kaimen] interface
各界[kakkai] each field
学界[gakkai] academic or scientific world
官界[kankai] bureaucracy