pernicious: implies irreparable harm done through evil or insidious corrupting or undermining: the claim that pornography has a ~ effect on society.  （insidious阴险潜伏的implies someone or something dangerous that develops gradually without being noticed,如insidious enemy/virus阴险的敌人，潜藏的病毒） (undermine（逐渐）损害，如削弱根基to make something weaker at the base gradually, for example by digging under it，如she undermined him and destroyed his confidence in his own talent她暗中逐渐打击他，让他对自己的才华失去信心）   pornography淫秽作品，如书刊音像制品


baneful: implies injury through poisoning or destroying influence: the ~ notion that discipline destroys creativity.


noxious: applies to what is both offensive and injurious to the health of body or mind: ~ fumes emanating from a chemical plant.    如their behaviour was noxious他们的行为令人生厌，这里noxious主要表示让人恶心。     emanate散发  


deleterious: applies to what has an often unsuspected or unanticipated harmful effect, especially on the living body: megadoses of vitamins can have ~ effects.   巨量


detrimental: implies something obviously, but not necessarily extremely, harmful to the thing it affects: the ~ effects of prolonged fasting.


pernicious恶性有害: 指造成难以挽回的恶性伤害，如腐蚀损害根基，baneful有毒: 指有毒的毁灭性的伤害，noxious恶心有害: 既让人恶心又有害健康，deleterious有害: 指一般怀疑不到预料不到会有害，detrimental有害: 指某物明显有害，但不是极其严重


记忆方法: 1）首字母PBNDD想成普遍能抵挡<==有害       （在《臣轨》一文中，武则天认为谋虑慎密、注重细节、早做准备、谨言慎行可以避免忧患祸害，原文如下："夫修身正行，不可以不慎。谋虑机权，不可以不密。忧患生于所忽，祸害兴于细微。人不慎密者，多有终身之悔。故言易泄者，召祸之媒也。事不慎者，取败之道也。明者视于无形，聪者听于无声，谋者谋于未成。不困在于早虑，不穷在于早豫。非所言勿言，以避其患；非所为勿为，以避其危。"）


        2）有害的意思是有伤害mean exceedingly harmful.