greek syntax principle 10

A PN will usually be anarthrous, and its subject articular.  It’s not always easy to know which is the subject and which the PN since they will be in the same case;  more in GGBB p42.

και ο λογος σαρξ εγενετο

When a pronoun is present, it will be the subject.

εγω ειμι ο Χριστος