The verb expressing"add/put in"is pronounced[tşαη]in some Mandarin dialects,and sometimes"□[tşαη]"is used as an instrumental preposition or a disposal marker equivalent to pingjie/yong,ba,rang/jiao/shi,etc.There is no convincing conclusion on the original form in writing and the evolution of"□[tşαη]".This paper mainly describes the pronunciation and the semantic functions of"□[tşαη]"based on data from dialects and literature,analyses the pronunciation,meaning and usage of"掌,长,着",the original forms in writing of"□[tşαη]"identified by some scholars.Based on this,the paper proposes that"□[tşai]"is more likely a syllable contraction of"着上".