TranSID is a tree-based SGML transformation language, which can also be used for other SGML processing: for performing queries and for limited formatting. An evaluator of the TranSID language has been implemented, and tested to run in the Linux and Solaris environments. This report serves as a reference manual of the TranSID language. The report describes the syntax and informal semantics of the language and its built-in functions, as of version 0.038 of the evaluator.