The TermBaum library provides an easy to use Tree representation of infix terms in JAVA. It handles term parsing, calculation, variables (i.e. function macros), derivation and simplification of functions. New functions can be dynamically added by writing small and simple plugins representing those functions. Since the representation is recursive, plugins only have to implement calculation and derivation of the new function itself. A small command line calculator is part of the distribution to show some features of the library.