Arabic language as one of Semitic Languages has a great number of speakers among the others due to usage of more than 20 countries such as Kuwait, Saudi Arabian, UAE, Egypt, Sudan, etc. It was only used to communicate between Arabian and developed becoming a language of Islam Religion. But Arabic is rich of vocabulary which is developed from a root then became and formed many words in different meanings. The word formation process into many different meanings interests the writer to research and write about it. This research discussed about the affixes in Arabic, the functions of the affixes, and the meaning which is generated by it. The writer conducted library research method to analyze and to conclude the aim of the researcher. Finally, the writer found that derivational affixes in Arabic are called al-ahrufaz-zaidah. Then, to form Arabic words using derivational affixes always involves vocalism depends on original letters of words, vocalism, and expected meaning. The writer also found that function of derivational affixes in Arabic is to derive any roots into the expected words and change its lexical identity. Later, these derivational affixes can be used to change the root which is transfixed into the past tense verb (v) to be a noun (n) and also the past tense verb (v) to be an adjective (adj.). Finally, the writer suggested next research of this term can be much better and make deeper analysis for better output and expectation.