skim就是 read sth quickly in order to find a particular point or the main point即快速閱讀以找到文章的中心思想/主要意思.
If you skim through the play too quickly,you'll forget the plot.
如果你讀劇本讀得太快,就會忘記劇中主要情節(jié).
scan就是 look at every part of sth carefully,especially because you are looking for a particular thing or person即快速閱讀以找到某一具體的信息
His mother scanned his face to see if he was telling the truth.
他母親察看他的面色看他是不是在講真話.
scan的意思：細(xì)看; 掃描; 粗略地看; 審視; 瀏覽; 符合格律,韻律合拍; 掃描,掃掠; 標(biāo)出詩的格律