詞根決定單詞意思，前綴改變單詞詞義，後綴決定單詞詞性。 英語單詞的構成有一定的規律，這些規律叫構詞法。主要有四種：合成、轉化、派生和縮略。常見的是前三種。

　　1. 合成

　　由兩個或兩個以上的詞合成為一個詞。

　　舉例：

　　Classroom，　newspaper

，　blackboard，　Schoolmate，newly-born，hardworkingpolice+man=policeman

　play+ground=playground，birth+day=birthday

　　after+noon=afternoon

　　hand+bag=handbag

　　every+where=everywhere

　　bed+room=bedroom

　　no+where=nowhere

　　hand+writing=handwriting

　　any+where=anywhere

　　grand+parent=grandparent

　　how+ever=however

　　what+ever=whatever



　2. 轉化

　　由一詞類轉化為另一詞類。

　　動詞walk、 talk、look、 swim etc.

　　在短語have a walk 、have a talk、 have a look、 have a swim etc中則轉化為名詞;

　　形容詞cool 、warm、 clean、etc可以轉化為動詞意為：使涼快、使溫暖、打掃等。

　　3. 派生法

　　①常用前綴 表“否定”

　　un- unfair unable unlikely, in/im- impossible impossible incapable, dis-discover disagree dislike dishonest 表“重複” re- rewrite retell repeat reconsider

　　②常用後綴 名詞後綴

　　-er/ or/-tion/ -ese/ -ist/ -ing/ -ment/ -ness/ -ian

　　“動作的執行者”名如：

　　teacher visitor inventor organization congratulation invention Chinese Japanese pianist scientist violinist living greeting wedding movement treatment happiness illness sickness carelessness 動詞後綴

　　–ify/-ice/-ise/-en 使…變… beautify/realize/ organize/sacrifice lengthen strengthen

　　形容詞後綴

　　–able/-ful/-y/-ive/-al/-an suitable comfortable movable beautiful careful useful sunny, windy, cloudy, snowy, sleepy, salty active, instructive musical medical physical American European Australian -ly

　　副詞後綴 carefully really certainly

　　數詞後綴 -teen 表“十三至十九” fourteen fifteen nineteen -ty 表“二十、三十…七十”