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

飛行の三鈷[higyounosanko] three-pronged vajra flung by Kukai on his return from China to determine the Holy Land of Esoteric Buddism
三鈷[sanko] trident vajra
独鈷[tokko] tokko

独鈷石[tokkoishi] ground stone tool from the late Jomon period (named after its similarity to the Buddhist tokko)
雷鈷[raiko] ground stone tool from the late Jomon period