γνῶσις
Gnosis
Spiritual knowledge — knowing through encounter, not reasoning
Gnosis in the Philokalia carries none of the problematic connotations of Gnosticism. It refers to the direct, experiential knowledge that comes through the nous rather than through discursive reason — knowing God not through reasoning about God but through direct encounter.
You can read about fire or you can put your hand near the flame. The first is dianoia. The second is gnosis. Diadochos of Photiki and Maximos the Confessor both describe gnosis as the fruit of sustained contemplative practice: a way of knowing that is qualitatively different from intellectual understanding, that the practitioner who has not experienced it can only read about and the practitioner who has experienced it can barely describe.