This paper discusses the modifying functions of two Turkmen morphemes -KA [-qa:/-ka:] and -Ay [-a:y/-a:y]. When added to the predicate of an interrogative sentence, these morphemes contribute to the meaning by conveying semantic notions of epistemic modality such as speculative epistemic possibility, predictive hypothetical content, dubitation, etc. Among these two markers, -KA is remarkable because it also can be inflected for person and number. Both the semantic and morphosyntactic features of these morphemes are analyzed.