(a) The complete relational diagram of all the possible two-terminal fundamental circuit elements, each defined by a direct relationship between two basic variables. It consists of four linear elements, the resistor (R), the capacitor (C), the inductor (L), the transtor (T), and four nonlinear memelements, the memristor (M_R), the memcapacitor (M_C), the meminductor (M_L), and the memtranstor (M_T). Symbols for transtor and memtranstor are introduced to facilitate later usage. (b) Schematic illustration of the memtranstor behaviors. The butterfly-shaped hysteresis loop is expected to occur at a sufficiently large input of q or φ.