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

ニュース媒体[nyuusubaitai] news media
圧力団体[atsuryokudantai] pressure group
安定同位体[anteidouitai] stable isotope
意識体[ishikitai] discarnate entity
為体[teitaraku] state of affairs

異性体[iseitai] isomer
異体[itai] different body
異体字[itaiji] kanji variants
移動体[idoutai] moving body
遺体[itai] corpse

グループ分離キャラクタ[guruupubunrikyarakuta] group separator
システム分析[shisutemubunseki] systems analysis
ファイル分離キャラクタ[fairubunrikyarakuta] file separator
ユニット分離キャラクタ[yunittobunrikyarakuta] unit separator
レコード分離キャラクタ[rekoodobunrikyarakuta] record separator

異分子[ibunshi] outsider
医薬分業[iyakubungyou] separation of medical and dispensary practice (practise)
一回分[ikkaibun] dose
一部分[ichibubun] part
一分[ichibu] one tenth

一系[ikkei] single-family lineage
家系[kakei] family lineage
革新系[kakushinkei] liberal
共産系[kyousankei] communist controlled
銀行系カード[ginkoukeikaado] bank issued credit card

系図[keizu] family tree
系図学[keizugaku] genealogy (the study)
系統[keitou] system
系統樹[keitouju] genealogical tree

異類[irui] varieties
一類[ichirui] same kind
円虫類[enchuurui] round worms
塩類[enrui] salts
塩類溶液[enruiyoueki] saline

貝類[kairui] shellfish
柑橘類[kankitsurui] citrus fruits
希土類[kidorui] rare earth
魚貝類[gyokairui] marine products
魚類[gyorui] fish