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

御守[omamori] charm
井守[imori] newt (esp. the Japanese fire belly newt, Cynops pyrrhogaster)
看守[kanshu] jailer
看守者[kanshusha] jailer
居留守[irusu] pretending to be out

見守る[mimamoru] to watch over
厳守[genshu] strict observance
固守[koshu] clinging
攻守[koushu] offense and defense
子守り[komori] babysitter