Collegian vs Collegial - What's the difference?

As a noun collegian

is a student (or a former student) of a college.

collegial.

(en noun)

A student (or a former student) of a college

(en adjective)

of, relating to, or ruled by colleagues

(Roman Catholic Church ) ruled by bishops having equal power

of or relating to a college or its students; collegiate

possessing adherence to the ethos, standards and conduct that govern behavior among colleagues within a given organization or profession

* collegially * collegiality