本の[honno] mere
異本[ihon] different edition
一坪本社[hitotsubohonsha] small company headquarters located in Tokyo simply for name value
一本[ippon] one long cylindrical thing
一本気[ippongi] single-minded (esp. personality or person)

一本橋[ipponbashi] (a) log bridge
一本建て[ippondate] (a) single standard
一本松[ipponmatsu] solitary pine tree
一本杉[ipponsugi] (a) solitary cryptomeria tree
一本槍[ipponyari] guiding principle

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