  In his paper "If it's pinched it's a memristor" [Semicond. Sci. Technol. 29,
104001 (2014)] L. Chua claims to extend the notion of memristor to all
two-terminal resistive devices that show a hysteresis loop pinched at the
origin. He also states that memcapacitors and meminductors can be defined by a
trivial replacement of symbols in the memristor relations, and, therefore,
there should be a correspondence between the hysteresis curves of different
types of memory elements. This leads the author to the erroneous conclusion
that charge-voltage curves of any memcapacitive devices should be pinched at
the origin. The purpose of this Comment is to correct the wrong statements in
Chua's paper, as well as to highlight some other inconsistencies in his
reasoning. We also provide experimental evidence of a memcapacitive device
showing non-pinched hysteresis.
