common/usual/ordinary/normal/abnormal
记忆：
1. common [ 5kCmEn ] 前缀com表示“共同，一起”, common adj. 共同的，常见的 It’s common that we find something in common with strangers.在陌生人间找到共同点也很常见。
2. usual [ 5ju:VuEl ] adj. 经常的 He often sits in his usual seat.他一般坐他通常的那个座位。
3. unusual [ Qn5ju:VuEl ] adj. 不寻常的，罕见的It’s unusual for him to give up the chance to go abroad.他放弃出国的机会，这很不寻常。
4. ordinary [ 5C:dinEri ] adj. 普通的，一般的 After all, we are ordinary people. Never wishes it would rain dollars. 我们毕竟是普通人。不要指望天上会掉馅饼。
5. extraordinary [ iks5trC:dnri, iks5trC:dinEri] adj. 非凡的 I saw an extraordinary painting at the exhibition center last week.上周我在展览中心看到了一张非凡的油画。
6. normal [ 5nC:mEl ] adj. 正常的，正常 Everything returned to normal soon. 不久，一切恢复正常。
7. abnormal [ Ab5nC:mEl ] adj. 不正常 It’s abnormal for the river to be so smelly. 河千发出如此的臭味，这很不正常。
另类阅读：
It’s normal that a common disease hits young people. As usual, we ordinary people must be careful.
轻松一刻：
A man saw a friend wearing a pair of crocodile shoes, and was very envious. When his friend told him they were very expensive, he was determined to hunt a crocodile himself.
He found a pond, jumped in and fought fiercely against a crocodile for a long time before he dragged it out to the ground.
Then a sigh was heard from him, "It's a great waste of time! The crocodile has worn no shoes at all!"