Pernicious means very harmful or evil, and often in a quiet way, so you do not notice the damage at first.

PerniciousPernicious means very harmful or evil意思是非常有害或邪惡， and often in a quiet way而且常常是悄悄地進行的， so you do not notice the damage at first所以你一開始不會注意到傷害。

A pernicious rumour can slowly ruin someone’s name. A pernicious habit can eat at your health for years before you see it.

A pernicious rumour一個pernicious的謠言 can slowly ruin someone's name可能慢慢毀掉一個人的名聲。 A pernicious habit一個pernicious的習慣 can eat at your health可能侵蝕你的健康 for years before you see it好幾年，你才會發現。

The word is formal and a little literary; you will hear it in essays, news, and medicine more than in the playground.

The word is formal and a little literary這個字正式、帶點文學味； you will hear it in essays, news, and medicine你會在論文、新聞和醫學裡聽到它， more than in the playground而不是在操場上。

In medicine, pernicious anaemia is a real illness name — a serious kind of anaemia — and that set phrase is worth knowing as a block.

In medicine在醫學上， pernicious anaemia is a real illness namepernicious anaemia是一個真正的病名—— a serious kind of anaemia一種嚴重的貧血—— and that set phrase is worth knowing as a block這個固定用語值得整個記起來。

Though actually, it does not mean “precious,” and it does not simply mean “annoying.” The harm is real and often deep.

Though actually不過其實， it does not mean "precious,"它不是"precious"（珍貴）的意思， and it does not simply mean "annoying."也不只是"annoying"（討厭）的意思。 The harm is real and often deep傷害是真實的，而且常常很深。