いとも簡単に[itomokantanni] very easily
一了簡[ichiryoukan] at one's discretion
簡易[kani] simplicity
簡易化[kanika] simplification
簡潔[kanketsu] brevity

簡素[kanso] simplicity
簡素化[kansoka] simplification
簡体字[kantaiji] simplified Chinese character
簡短[kantan] simple
簡単に言うと[kantanniiuto] simply put

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