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.)

アナログ計算機[anarogukeisanki] analog computer
シフト演算機構[shifutoenzankikou] shift arithmetic unit
暗算[anzan] mental arithmetic
違算[isan] miscalculation
一般命令演算機構[ippanmeireienzankikou] general instruction unit (computer)

運算[unzan] mathematical operation
演算[enzan] (mathematical) operation
演算機[enzanki] processor (as in computer chip)
演算子[enzanshi] operator
演算手順[enzantejun] algorithm