御三時[osanji] three-o'clock snack
三鞭酒[shanpen] champagne
球面三角法[kyuumensankakuhou] spherical trigonometry
胸三寸[munesanzun] heart
元三[ganzan] New Year's period (January 1st to 3rd)

五十三次[gojuusantsugi] the 53 Toukaidou stages
向こう三軒[mukousangen] one's next three neighbors
降三世明王[gouzanzemyouou] Trailokyavijaya Vidya-raja
再三[saisan] again and again
再三再四[saisansaishi] repeatedly

運輸省[unyushou] Ministry of Transport
外務省[gaimushou] Ministry of Foreign Affairs
各省[kakushou] each ministry
冠省[kanshou] Forgive me for dispensing with the preliminaries, but I hasten to inform you that...
帰省[kisei] homecoming

教育省[kyouikushou] Department of Education
省みる[kaerimiru] to look back (e.g. over shoulder or at the past)
厚生省[kouseishou] Ministry of Health and Welfare (now Ministry of Health, Labour and Welfare)
国防総省[kokubousoushou] National Military Establishment
国務省[kokumushou] State Department