ob-来自拉丁介副词ob，原意是toward，在构词当中又引申出against, inversely等意思。ob-是个原生词缀，一般与拉丁词根缀合，所构成的派生词的词性取决于词根或后缀的属性。由于语音的同化作用，ob-在c，f，p前面，变成oc-，of- , op-。在元音字母及其他辅音字母前，ob-形态不变。

现先各举一例说明ob-出现在各种字母前的情况。 

obey [ob- = toward 向；ey (aud) = to listen 听=>“to listen toward 听从”→]v. follow the orders of 听从，服从 / We only obey our leader. 我们只听领导的。

obedience n. 服从，顺从 

obedient a. 服从的，顺从的，恭顺的

obdurate [ob- = against 对抗；dur = hard 硬的；-ate a. = being =>“being hard against 硬顶着的”→]a. stubborn or unyielding 倔强的；顽强的/ He is an obdurate criminal. 他是个顽固不化的罪犯。

obduracy n. 倔强；顽固

object [ob- = against 对着；ject = to throw 扔=>“to throw sth. against将某物对…扔去”→“oppose sth. to以某物相对抗”→]v. be opposed 反对 / Many people object to the proposal. 许多人反对该建议。

objection n. 反对，异议；不喜欢

oblige [ob- = toward 向；lig = to bind 束缚；-e=>“to bind sb. toward sth. 将某人束缚在某物上”→]v. bind by a promise, contract or duty; compel 以誓言、契约、责任等束缚；迫使/The law obliges parents to send their children to school. 法律责使父母送子女上学。