前綴over-的前身是英語介副詞over, 它的基本意思是 above (在…之上），由此又引申出across (越過），too (太），too much (過分）等意思。over-作為修飾性的派生前綴，能與形容詞 (或分詞）、名詞及動詞綴合，一般不改變詞基單詞的詞性。over- 與形容詞（或分詞）結合時，意思大致為too;與名詞結合時，意思大致為over, above (這時詞基的詞性可能發(fā)生變化）或too much, excessive;與動詞結合時，意思大致為over或too much。

先介紹幾個over-與形容詞（或分詞）結合的詞例。

overactive [over- = too 太; active a. 活躍的→]a. too active; active to excess 過于活躍的 / Most of the children there were overactive, overirritable and doing poorly scholastically. 那兒的大多數兒童都多動，過于易怒，學業(yè)都很差。

overdue [over- = too 過分；due a. 到期的=>“too due 過分到期了”→] a. more than due; due some time ago but not yet paid 過期的；到期未付的/This bill is overdue.這張支票過期了。

overbearing [ over- = too 過分；bearing a. 壓制的=>“too bearing 過于壓制人的”→]a. forcing others to one's own will；masterful 好壓制的；專橫的 / We found it hard to like the new teacher because of his overbearing manners. 我們覺得很難喜歡上新來的老師，因為他作風專橫傲慢。

接著介紹over-與名詞綴合的（改變詞性與不改變詞性）兩種情況。

overboard [ over- = across 越過；board n. 船舷=>“across the board 越過船舷的”→]ad. from ship or boat into water 從船上落人水中 / The sailor slipped and fell overboard. 那船員滑了一跤落人水中。 

overhead [ over- =above 在…上；head n. 頭→]ad. over the head; far above 在頭頂上；架空的 / You can see a cableway overhead. 你能看到頭頂上有條高架索道。