ἡσυχία
Hesychia
Stillness — the tradition's namesake
The tradition's word for the deep, alert stillness that contemplative prayer cultivates. It is what gives the entire tradition its name — hesychasm is the practice of hesychia, a hesychast is a practitioner of stillness.
This stillness is not what you might expect. It is not the absence of sound, not the suppression of thought, not the blank-screen emptiness that some forms of meditation pursue. Gregory of Sinai described it as requiring "above all faith, patience, love with all one's heart and strength and might, and hope." That is a remarkably active list of requirements for something called stillness. Isaac of Syria called it "the mystery of the age to come." Hesychios called it "the heart's stillness" — an interior condition, not an external circumstance.
The tradition draws a clear distinction between external silence — being in a quiet place — and interior hesychia — the heart at rest in God's presence. You can be in complete external silence and have a mind churning with worry. You can be in the middle of a crowded street and carry hesychia in your heart. The first is a helpful condition. The second is the actual goal.
For the tradition, hesychia is not a technique but a quality of being. You don't "do" stillness — you enter it, or more precisely, you discover it was always there beneath the noise. The prayer and the watchfulness clear away the clutter. What remains is hesychia — the natural condition of the heart when it is no longer agitated by unchecked thoughts and passions.