確かに[tashikani] surely
確かめる[tashikameru] to ascertain
確言[kakugen] assertion
確乎[kakko] firm
確執[kakushitsu] discord

確実[kakujitsu] certainty
確実性[kakujitsusei] certainty
確実度[kakujitsudo] certainty
確証[kakushou] positive proof
確信[kakushin] conviction

安全保障条約[anzenhoshoujouyaku] US-Japan Security Treaty
違約[iyaku] breach of contract
違約金[iyakukin] penalty for contract breach
一粒子既約[ichiryuushikiyaku] one particle irreducible (physics)
化学兵器禁止条約[kagakuheikikinshijouyaku] chemical weapons ban treaty

仮条約[karijouyaku] provisional treaty
会う約束[auyakusoku] rendezvous
会員規約[kaiinkiyaku] membership agreement (e.g. for a credit card)
解約[kaiyaku] cancellation of contract
確約[kakuyaku] firm promise