Clitic is an interface structure between semantic and syntax. In the same time, clitic has got both noun and verb features. Its syntax is linked with the theta-role configuration and its morphology is rich like a noun. The behavior of clitic has peculiar phenomena, i.e. climbing, and differences concerning the position of clitic and verb. There are many differences between proclitic (clitic before verb) and enclitic (clitic after verb). Classical generative syntactic models tried to explain these differences, but a best account of clitic phenomena is gift by OT models. In first and second chapters of my work, I introduce clitic in typology and the most relevant theories to justify its syntactic nature. Then, in third, 4th and 5th chapters, ...