Lasciviousness is the noun: the quality, or the behaviour, of being lascivious. Writers talk about the lasciviousness of a scene, or accuse someone of lasciviousness. It names the thing itself — the wanting, the tone, the conduct — not the person. Like lascivious, it is formal and usually critical. You will almost never hear it in casual conversation; it lives in essays, reviews, and sometimes in legal or moral language. Though actually, because the word is so heavy, using it about a person can sound more like a charge than a description, which is why careful writers often attach it to a look, a scene, or a style rather than to someone’s whole character.

淫蕩、好色（指這種性質或行為，不是用來叫某個人）