His all-day sulkiness after losing the match made his teammates afraid to talk to him.

sulkiness 是由形容词 sulky（闷闷不乐的）加上名词后缀 -ness 构成的名词形式。sulky 来自动词 sulk（生闷气），加上形容词后缀 -y 表示"具有...特性的"。sulkiness 指"闷闷不乐的状态或情绪"。