复习资料（3.2）
2、Types of morphemes 语素的分类
a)Free morphemes 自由语素
Free morphemes are the morphemes which are independent units of meaning and can be used freely all by themselves or in combination with other morphemes.
自由语素是独立的意义单位，能够独自自由使用，当然也可以和其它语素结合使用。
b)Bound morphemes 黏着语素
Bound morphemes are the morphemes which cannot be used independently but have to be combined with other morphemes, either free or bound, to form a word.
黏着语素是那些不能单独使用，而必须和其它语素－自由语素或黏着语素－结合在一起以形成一个单词的语素。