Non-binary - is a much newer phrase that seems to be emerging that cuts past the fashion aspect (androgyny) and goes to the fundamentals of gender identity. Thank you Stanna for linking us to the article “Is Trans Over”.
According to Dictionary.com, “Trans-“ is a prefix occurring in loanwords from Latin ( transcend; transfix); on this model, used with the meanings “across,” “beyond,” “through,” “changing thoroughly,” “transverse,” in combination with elements of any origin.
Thus in accepting the proper definition, “Transgender” denotes crossing/moving from one gender to another. Being male and presenting as female - Being female and having surgeries to bring your body into congruence with your male mental perception. Vice versa, certainly applies.
Non-binary describes a gender identity, which does not fit the male and female binary. Thus transcending male and female identities; not crossing or moving from either. Separate and different from transgender. Although space under the transgender umbrella is available, I am not sure that transgender is how non-binary individuals see themselves.
Riki Wilchins in the Advocate article concluded with this statement:
… What comes next, what takes its place, is going to be very interesting. We are unconsciously and finally treading toward the end of gender. In my opinion, that step is long overdue.
Maybe transgender it was only a resting point in our human social evolution. I see myself as a transgender person and I am happy to find this confront point. Riki's article is an interesting concept to consider.