How many types of motivation are there in English? Give ONE example for each type.

There are four types of motivation: 1）Onomatopoeic motivation, e.g. cuckoo, squeak, quack, etc. 2）Morphological motivation, e.g. airmail, reading-lamp, etc. 3）Semantic motivation, e.g. the mouth of the river, the foot of the mountain, etc. 4）Etymological motivation, e.g. pen, laconic, etc.