下位互換性[kaigokansei] downward compatibility
互い[tagai] mutual
互いに[tagaini] mutually
互い違い[tagaichigai] alternate
互い違いに[tagaichigaini] alternate

互に[katamini] mutually
互角[gokaku] equality
互換[gokan] transposition
互換性[gokansei] compatibility
互恵[gokei] reciprocity

お生憎様[oainikusama] that's too bad (ironical)
御誕生日おめでとうございます[otanjoubiomedetougozaimasu] Happy Birthday
隣の芝生は青い[tonarinoshibafuhaaoi] the grass is always greener on the other side
生きがいい[ikigaii] fresh (e.g. fish)
コンピューター援用生産[konpyuutaaenyouseisan] computer-aided manufacture

委託生[itakusei] scholarship student sent by government office or business
生す[nasu] to build up
異常発生[ijouhassei] plague
医学生[igakusei] medical student
医学生物学[igakuseibutsugaku] medical biology