Modality is a category that reflects the speaker's attitude, stance, and mental state regarding an event or situation and has various indicators. From the earliest studies on modality in linguistics to the present day, there has been uncertainty about how it should be defined and according to which criteria it should be classified. Probabilistic modality is one of the types of modality classified under the heading of proposition, signifying semantic meaning fields such as prediction, assumption, doubt, uncertainty, indefiniteness, and certainty. Our study consists of examining markers that fall within the semantic field of probability in the books Altun Yaruk, Altun Yaruk IV, Altun Yaruk IV, Altun Yaruk VIII, and Altun Yaruk X, written in Old Uyghur and published in Turkiye, which deal with Buddhism and Buddhist philosophies. There are numerous markers of probability mood in Altun Yaruk. The lexical markers examined in the study are antag yme, azu, alku üd, odgurak, odguratı, seziksiz, seziksizin, turkaru, ürüg ürgüt, ürüg uzatı; the morphological markers are -GAy, -DAçI and the lexic and morphological markers are birök...-sAr, unkalı..-GAlI and syntactic markes are kim and mU are question enclitics. Although the identified elements are seen to be words functioning as adjectives, adverbs, copulas, etc., or inflectional elements in the sentence, it can be said that they are markers responsible for conveying the semantic meaning domain of probability (low probability, uncertainty, proximity to certainty, and certainty, etc.).

Modality, possibility modality, Old Uyghur, Altun Yaruk.