Mark (skopeite). Keep an eye on so as to avoid. Skopos is the goal, skopeō means keeping your eye on the goal.
Divisions (dichostasias). Old word for “standings apart,” cleavages. In N.T. only here and Gal 5:20.
Those which are causing (touṡ̇poiountas). This articular participle clause has within it not only the objects of the participle but the relative clause hēn humeis emathete (which you learned), a thoroughly Greek idiom.