Essence refers to the inside story, which refers to the truth revealed after removing the disguise; Nature refers to the type, which refers to what type the whole event belongs to, including the true and false parts. For example, the essence of 9 1 1 incident is the terrorist massacre carried out by terrorist tycoon bin Laden, which is vicious, unpopular and arouses public anger. Content words are generally nouns and objective statements, while qualitative words are generally adjectives with subjective value judgments.