and their formation as well as their relationship to other words in language. The four skills of language are integrated and not isolated that’s why knowing to write needs the command of knowing how words structured and related to one another. Affixation is the smallest part of morphology which studies the form and the change of words. Millward and Hayes (2011:4) mentioned that most derivational prefixes simply change the meaning of the word it is attached to while others change the class of the word. Derivational suffixes change the word class category which in turn changes the meaning of the word to which it is attached. This study investigates the use of Affixation (prefixes and suffixes) for level 8, 9 and 10 EFL students at King Khalid University and how the use of appropriate Affixation enhances the learners’ writing paragraphs. The data was collected through a test administered to 60 EFL students. The data analyses were done by the statistical package for social sciences (SPSS) program.