Lechery is strong sexual desire, talked about as a bad thing. The word does not just say 'this person wants sex' — it carries the speaker's judgement, that the wanting is greedy, ugly, and pointed at people the person has no real feeling for. It belongs to an old moral vocabulary: in the Christian list of seven deadly sins, lechery is the older English name for the sin now usually called lust. That is where most students will meet it — in old books, sermons, history, Shakespeare, or writing that is deliberately reaching for that old sound. Almost nobody says it in ordinary conversation today. If a friend tells you about someone at work who keeps staring, they will say he's a creep, or he's disgusting — not 'his lechery'. Because it is a noun, it names the quality or the behaviour as a whole, not one act: you write about the lechery of a court, of an old king, of a whole society. It is worth knowing one thing about how the word has drifted. In older use it could be quite serious — real sexual wrongdoing, seducing people, ruining lives. In modern use, when it appears at all, it is often lighter and half-joking, describing an old man who leans too close and says things he should not: more pathetic than dangerous. So the same word can be an accusation or a wry smile, and only the surrounding sentence tells you which. The related words are more common than the noun: a lecher is such a person (usually an older man), and lecherous is the adjective, which you will meet far more often than lechery itself.

好色、淫慾。在宗教脈絡中就是七宗罪裡的「色慾」那一項（現在多譯作 lust）。台灣學生看到這個字多半是在文學或歷史翻譯裡，日常講某人很色會說「色鬼」「鹹濕」，不會用到這麼書面的詞。