θυμός
Thymos
The incensive power — the soul's faculty of resistance
Thymos is one of the three faculties of the soul in the Philokalia's anthropology (along with the desiring faculty and the rational/intellective faculty). It's the source of energy, resistance, and indignation — the part of you that fights back, pushes through difficulty, and refuses to accept what is wrong.
When functioning properly, thymos provides the energy needed for the spiritual struggle — the determination to resist destructive patterns, to persevere in prayer when distracted, to stand firm against discouragement. When distorted by the passions, it becomes rage, resentment, bitterness, and aggression.
The tradition's teaching is that thymos should not be eliminated but redirected. Isaiah the Solitary taught that "there is among the passions an anger in accordance with nature" — a righteous anger directed not at other people but at the destructive patterns within yourself. This is thymos functioning as it was designed to: providing the energy for inner transformation.