1. A system for building an interface that receives and responds to varied natural language expressions, the system comprising: at least one hardware processor; and at least one executable module that, when executed by the at least one hardware processor, builds at least one data structure comprising a plurality of sets of data fields that contain a plurality of concept symbols, wherein the plurality of concept symbols comprise a plurality of elementary concept symbols, wherein each of the plurality of elementary concept symbols corresponds to a natural language element, and a plurality of compound concept symbols, wherein each of the plurality of compound concept symbols corresponds to a pair, wherein the pair comprises one of a first elementary concept symbol and a second elementary concept symbol, an elementary concept symbol and a compound concept symbol, or a first compound concept symbol and a second compound concept symbol, wherein each of the plurality of concept symbols identifies a set of data fields, and wherein each set of data fields represents a mental concept and comprises an ordering field comprising an ordinal number value that orders the set in order of its creation in the at least one data structure, an outline field comprising an ordinal number value that assigns the set to its location in the at least one data structure in an overall outline format, a vocabulary field that is either empty or comprises a natural language element corresponding to the concept symbol, a concept field comprising the concept symbol, a lookup field that is either empty or comprises a pair of concept symbols corresponding to the concept symbol, a response field that is either empty or comprises one or more symbols that each identify a response action, and an action field that is either empty or defines a response action.