1) common “普通的”,“平常的”,“共有的”,指从质量或品德上无特殊,显眼或杰出之处,因而是大多数人或事物所具有的,常见的.
It’s an error quite common among schools.
This flower is common in spring.
2) ordinary 指符合一般或常规事物标准或相同的规格,因而只具有普通的特性.例如：
Although he is rich,he is always in ordinary dress.
common与ordinary基本同义,强调“平凡的,普通的”,表示随时可以碰到,不值得惊奇.如：
an ordinary ( a common) event 常有的事情
an ordinary (a common0 person 一个普通的人
3) usual 通常与人的行为习惯有关,含义为“惯常的,通例的”.例如：
Tea is considered to be the usual drink of British people.
He arrived later than usual.
4) general 意为“普遍的”、“一般的”,与高级想对应.例如：
This book is intended for the general reader,not for the specialist.这本书是为一般读者写的,不是为专家写的