selfish是形容词词性，自私的

①它的名词形式为selfishness

He argued that the overcrowded cities were the product of a system based on "selfishness" and "rapacity."

他辩称说，过分拥挤的城市是建立在“自私”和“贪婪”基础上的制度造成的。

②它的副词形式为selfishly

Someone has selfishly emptied the biscuit jar.

有人自私地吃光了饼干罐里的饼干。