劍橋詞典

added to adjectives to form nouns that refer to a quality or a condition
（與形容詞連用構(gòu)成名詞表示性質(zhì)或狀態(tài)）
happiness 高興
sadness 悲傷
nervousness 緊張
selfishness 自私
kindness 友善 返回 -ness