Simplicity
This paper neatly summarises various results about the simplicity of axiomatisations or formal languages (in the sense in which theories are usually given by presenting a set of predicate (or relation) symbols and a set of function (or operation) symbols as the language of the theory). The paper cites various results about simplicity taken as syntactical, and presents a number of open problems about simplicity taken as semantical.
scientific article; zbMATH DE number 4095424