Common 用于是通常的、常发生的、广泛使用或众所周知的：
a common problem;
共同的问题；
a common thief;
普通的小偷；
the common dandelion.The term also suggests lack of distinction and can imply coarseness or crudeness:
普通的蒲公英.此词条也暗示缺乏区别并能意指粗劣或未加工：
drank wine of the commonest sort;
最为普遍的饮用葡萄酒；
had a very common look about him.
他有着很普通的外表.
Ordinary describes what is of the usual kind and is not distinguished in any way from others.In the latter sense it is sometimes derogatory:
Ordinary 指种类普通且不能从其他中加以区别的.在后一意义上,它有时是贬义的：
A ballpoint pen is adequate for most ordinary purposes.
原珠笔适合最普通的用途.
The violinist gave a very ordinary performance marked by an occasional memory lapse.
小提琴手因偶然记忆失误表现很平常.
Normal stresses adherence to an established standard,model,or pattern:
Normal 强调符合已建立的标准、模型或方式：
normal body temperature;
正常体温；
normal curiosity.
正常的好奇心.