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

おけさ節[okesabushi] style of Japanese folk song associated with Niigata Prefecture
双節棍[nunchaku] nunchaku (two linked fighting sticks)
一音節[ichionsetsu] monosyllable
一節切り[hitoyogiri] one-jointed bamboo musical instrument
音節[onsetsu] syllable

鰹節[katsubushi] katsuobushi
環節[kansetsu] segment (of worm)
関節[kansetsu] joints (knee joint, elbow joint, etc.)
関節リューマチ[kansetsuryuumachi] rheumatoid arthritis
関節炎[kansetsuen] arthritis

意味深重[imishinchou] with profound (often hidden) meaning
一重ね[hitokasane] suit
一重継ぎ[hitoetsugi] sheep bend (knot)
一重桜[hitoezakura] cherry tree bearing single blossoms
荷重[kajuu] load

過重[kajuu] overweight
気が重い[kigaomoi] depressed
貴重[kichou] precious
貴重品[kichouhin] valuables
起重機[kijuuki] crane

機関[karakuri] mechanism
に関して[nikanshite] related to
に関する[nikansuru] related to
シグモイド関数[shigumoidokansuu] sigmoid function
スカッシング関数[sukasshingukansuu] squashing function

ステップ関数[suteppukansuu] step function
ブーリアン関数[buuriankansuu] Boolean function
意志決定機関[ishiketteikikan] decision-making body
医療機関[iryoukikan] medical institution
因果関係[ingakankei] consequence