His belief in his own invincibility made him fearless in the competition.

invincibility 是由形容词 invincible（不可战胜的）加上名词后缀 -ity 构成的名词形式。invincible 本身由前缀 in-（表示否定）和词根 vincible（可战胜的）组成，vincible 来自拉丁语 vincere（战胜）。所以 invincibility 的意思是"不可战胜性"或"无敌"。