The Difference of Vocabulary Richness in Al-Sahifah Al-SajjadiyyahBase on Theories of “Yule” et al. and “Johnson”

One of the most important ways to understand people's thoughts is to study their written works. Each author draws a method consistent with his or her desired goals in order to affect the minds of readers. The style plays an important role in content transfer and access to the purpose of writing, because the readers’ inclination to read texts depends a lot on the proper structure of sentences. The most important modern trends are Stylistic that has multiple approaches, including Statistical Stylistics, a trend that uses quantity to achieve quality. This research deals with the study of Statistical Stylistics in Al-Sahifah Al-Sajjadiyyah. Ten prayers based on their words and subjects were selected and then compared their vocabulary richness, according to the two theories propounded by Yule and his colleagues, and Johnson, through descriptive-analytical and statistical approaches. We concluded that the highest vocabulary richness of Al-Sahifah Al-Sajjadiyyah is for the prayer 19 (Johnson's theory), and prayers 19 and 29 (by theory of Yule et al.), and the lowest is for the prayer 38 (Johnson’s theory), and the prayers 38 and 54 (by theory of Yule et al.). Thus, according to the two theories, the highest vocabulary richness is related to the moral category and the lowest is related to the historical category, but the differences between them was not much, and the reason of this differences have been the impact of social conditions.