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

御構いなく[okamainaku] please don't fuss over me
サーボ機構[saabokikou] servomechanism
シフト演算機構[shifutoenzankikou] shift arithmetic unit
ヒグス機構[higusukikou] Higgs mechanism (physics)
遺構[ikou] remains

一向に構わない[ikkounikamawanai] doesn't care at all
一般命令演算機構[ippanmeireienzankikou] general instruction unit (computer)
機構[kikou] mechanism
気構え[kigamae] readiness
虚構[kyokou] fiction

一段[ichidan] more
一段動詞[ichidandoushi] ichidan verb (one of the two main conjugation classes of verbs in modern Japanese, usually ending in -eru or -iru)
一段落[ichidanraku] completing the first stage
階段[kaidan] stairs
格段[kakudan] special

計画段階[keikakudankai] planning stage
決済手段[kessaishudan] method of payment
減段[gentan] reduction (of crop size)
五段[godan] Japanese verb group
五段動詞[godandoushi] godan verb (one of the two main conjugation classes of verbs in modern Japanese, usually ending in -u, -ku, -su, -tsu, -gu, -bu, -mu, etc.)