Prefixation and suffixation are two subclasses of affixation. Pl

Prefixation and suffixation are two subclasses of affixation. Please define prefixation and suffixation and explain the difference between them. Use “polite—impolite”, “happy—happiness” to illustrate your point.
【正确答案】：(1) According to the positions which affixes occupy in words, affixation falls into two subclasses: prefixation and suffixation. Prefixation is the formation of new words by adding prefixes to stems. Suffixation is the formation of new words by adding suffixes to stems. (2) The difference between them: prefixes do not generally change the word-class of the stem but only modify its meaning. Suffixes have only a small sematic role, their primary function being to change the grammatical function of stems. In other words, they mainly change the word class. For example, im- is the prefixation, and change the meaning of polite, while -ness is the suffixation, it does not change the meaning of happy, but its grammatical function.
【题目解析】：本题考查第四章前缀与后缀的联系与区别。考生需要对前缀与后缀非常熟悉的掌握，才能更好的应用。