Öz
According to Universal Grammar, postpositions are words that are at the head of postpositional phrases. Some case suffixes are used in the process of coming together with the words in the position of complement of the postpositional phrases. The concept of valency (valenz) is at issue here. That is, a postposition determines with which case suffix the complement should be connected to itself, based on Chomsky's government theory, during the formation of the phrase. From the point of view of the concept of valency and government, postpositions have semantic features in the lexicon and postpositions reflect these features in the phrase. In addition, valency is a concept used to express the semantic and syntactic features that words need to complete meanings in their deep and surface structure. In this respect, phrase structure rules are also determined in syntactic structure due to the valency of postpositional phrases. In this study, the time postpositions, which are among the ‘son çekim edatları’ according to the accepted view in the literature, are discussed in Tuvan, one of the Southern Siberian Turkic languages. Many ‘time postpositions’ are mentioned in the studies on Tuvan. In this study, the postpositions beer “since”, tura “since” bilek “as soon as”, çedir “until”, and deer “until”, which are accepted as time postpositions according to the Universal Grammar approach, are discussed. In the study, which case suffixes are required by the time postpositions and the semantic contribution of these suffixes to the postpositional phrases, as well as the syntactic reflections of valency of the postpositional phrase in sentence and phrase structure rules are examined.