2after“…时间后”结构：after+时间段，常用于一般过去时，和1相同。

　　They went to Beijing after five days. The dog died after a week.

　　(after也可加句子, 但主句不一定用一般过去时：I’ll send you an e-mail after I get home.

　　Return it to me after you finish it. 见2.)

　　3ago“…时间前”结构：时间段+ago, 用于一般过去时。

　　The Greens moved to Shanghai four weeks ago. I saw it ten minutes ago.

　　(若有since+时间段+ago，常用现在完成时：Mr. Li has worked here since 5 years ago.)

　　4before 单独放在句尾，常用现在完成时：“以前”

　　I have been to London before. He has seen the film before.

　　(若是时间段+before,常用过去完成时，“…前”： I had seen the film two weeks before. We had found out the answer to the problem an hour before.)

　　19.四季：spring春;summer夏;autumn秋;winter冬;season季

　　20.月：January, 一月; February, 二月; March, 三月; April, 四月; May, 五月;

　　June, 六月; July, 七月; August, 八月; September, 九月; October, 十月;

　　November, 十一月; December, 十二月。

　　21.星期：Sunday, 周日;Monday, 周一;Tuesday, 周二;Wednesday, 周三;Thursday, 周四;Friday, 周五;Saturday, 周六。Sunday是一周的第一天， Saturday是最后一天。

　　22.“也”：either, 用于否定句的末尾。also, 通常挨着动词，少用于句尾。too, 通常在句尾，前常有逗号。as well, 只用于句尾, 前无逗号。 注意：后三个词都不用于否定句。