注意如果用于过去时,用after+时间.ShewenttoNanjinglastMay,andshecamebackafteramonth.去年五月她去了南京,一个月之后她又回来了.大多用在将来时（一般将来时和过去将来时）.inanhour一小时之后inaweekorso一个多星期之后Hewillbebackinfivehours.他五小时之后回来.
Theysaidtheywouldarrivehereinaweek.他们说他们一周后到达.
比较within和inwithin强调在……时间之内,没有时态的限制.in是以现在为基准,inanhour是指从现在起1小时之后,所以一般只用于将来时.within3hours3小时之内Imustfinishpaintingthecatwithinfiveminutes.我必须在五分钟之内画好这只猫.Theyworkedhard.Theyfinishedtheworkwithin2daysatlast.他们努力工作,结果终于他们在两天之内完成了这项工作.