忍耐【にんたい】
endurance, perseverance, patience
忍者【にんじゃ】
ninja, person trained in ninjutsu and employed for covert purposes in feudal Japan
残忍【ざんにん】
brutal, cruel, merciless, ruthless, cold-blooded
忍ぶ【しのぶ】
to conceal oneself, to hide, to endure, to bear, to stand, to put up with