accidental, incidental, adventitious They all mean not being part of the real or essential nature of something.
它们都指不是事物真正的或基本的实质内容。
accidental 英 [ˌæksɪˈdentl] 美 [ˌæksɪˈdɛntl] retains its basic notion of chance occurrence but may also imply nonessential character.
它保留了偶然性的基本含义，但也指非本质的特性。(反)essential
例子：It could plausibly be argued that this diversity is accidental. 人们可以貌似有理地争辩说，这一差异是属于偶然性的。
cad, cas, cid=fall,表示”落下,降临”
1 ：accidental偶然的 2：decaent 颓废的 3：coincide 巧合,同时发生 4：incidentaladj. 附带的；偶然的；容易发生的
incidental 英[ɪnsɪ'dent(ə)l]美['ɪnsə'dɛntl]suggests a real, sometimes a designed, relationship but one which is secondary andnonessential.
它表示真正的(有时是计划好的)、但又是次要的、非本质的关系。(反)essential
At the bottom of the bill, you will notice variousincidentalexpenses such as faxes.
例子：在账单底部,你会发现有传真等各项杂费。
adventitious 英 [ˌædvenˈtɪʃəs] 美 [ˌædvɛnˈtɪʃəs, -vən-] implies a lack of essential relationships and may suggest casual addition orirrelevance.
它指缺少内在的联系，也可表示偶然的增加或表示无关。(反)inherent
例子：The court tries to understand whether the young man's misconduct was adventitious or the result of some serious flaw in his character.
法庭想弄明白这个年轻人的错误行为是偶然犯下的还是他性格中固有的缺陷造成的
ven,vent=come,表示”来”
1：adventitious a 偶然的,不定的 2:prevent v 防止,阻止 3 :contravene v 违反