一も二も無く[ichimonimonaku] unhesitatingly
一言二言[hitokotofutakoto] a word or two
一石二鳥[issekinichou] killing two birds with one stone
一二に及ばず[ichininioyobazu] right away
一姫二太郎[ichihimenitarou] It's good to have a girl first and then a boy

うり二つ[urifutatsu] as alike as two melons (two peas in a pod)
黄道十二宮[koudoujuunikyuu] twelve signs of the zodiac
二度[futatabi] again
最小二乗法[saishounijouhou] least-squares method
三十二分音符[sanjuunibuonpu] 32nd note

亜種[ashu] subspecies
異機種[ikishu] heterogenous equipment
異種[ishu] different kind (species, variety)
育種[ikushu] (plant) breeding
育種家[ikushuka] (plant) breeder

育種所[ikushujo] (plant) nursery
一種[isshu] species
一粒種[hitotsubudane] an only child
種違い[tanechigai] half-brother
艶種[tsuyadane] love affair

安全第一[anzendaiichi] safety first
及第[kyuudai] passing an examination
及第者[kyuudaisha] successful examinee
及第点[kyuudaiten] passing mark
次第[shidai] dependent upon

次第に[shidaini] gradually (progress into a state)
次第書き[shidaigaki] printed program
式次第[shikishidai] program of a ceremony (programme)
手当たり次第[teatarishidai] using anything one can lay one's hands on
出来次第[dekishidai] as soon as completed

誤魔化し[gomakashi] hanky-panky
間誤付かせる[magotsukaseru] to fluster
間誤付く[magotsuku] to be confused
誤ち[ayamachi] fault
誤つ[ayamatsu] to err

過誤[kago] mistake
確率誤差[kakuritsugosa] random error
見誤る[miayamaru] to mistake someone for someone else
個人誤差[kojingosa] personal equation
誤り[ayamari] error

に過ぎない[nisuginai] no more than
マルコフ過程[marukofukatei] Markov process
為過ぎる[shisugiru] to overdo
一過[ikka] passing away
一過性[ikkasei] transient (pain or fever)

過ぎ[sugi] past
過ぎる[sugiru] to pass through
過ぎ去った可能性[sugisattakanousei] might-have-been
過去る[sugisaru] to pass
過す[sugosu] to pass (time)