Complete the following statements with proper words or expressio

Complete the following statements with proper words or expressions according to the course book.The formation of words by adding word-forming affixes to stems is called ( ). 
【正确答案】：AFFIXATION
【题目解析】：本题考查词缀法的概念。词缀法(affixation)：在词干上增加词缀的构词方法称为词缀法。故空格处填写affixation。