小试牛刀

Use some examples to illustrate one of the forms of word formation——derivation.

参考答案：

Derivation forms a word by adding an affix to a free morpheme. Since derivation can apply more than once, it is possible to create a derived word with a number of affixes. For example, if we add affixes to the word friend, we can form befriend, friendly, unfriendly, friendliness, unfriendliness, etc. This process of adding more than one affix to a free morpheme is termed complex derivation. 

Derivation does not apply freely to any word of a given category. Generally speaking, affixes cannot be added to morphemes of a different language origin. Derivation is also constrained by phonological factors. Some English suffixes, most of which are Latin origin, also change the word stress.