The absence or suppression of feeling, motivation, and concern.
The absence or suppression of feeling, motivation, and concern — a deadening of interest and emotional response.
The wholesale dulling of feeling and drive (“voter apathy”) — set apart from indifference (not caring which way things go), impassivity (showing no outward trace of feeling at all), and, crucially, from equanimity, which is a regulated, positive calm, NOT a lack of feeling. Apathy is the negative absence of affect; equanimity is steadiness amid affect. Compare acedia (a spiritual torpor) and ennui (weariness from boredom).
From Greek apatheia, from apathēs “without feeling” (a- “without” + pathos “feeling, suffering”), via Latin apathia; into English c. 1600.
A documented reversal of valence: it entered English (c. 1600) meaning the prized Stoic ideal of freedom from disturbing passions; the now-dominant pejorative sense, “indifference to what should excite,” is dated to 1733.
Often loosely equated with calm or detachment — but in Stoicism apatheia was a positive ideal (freedom from passion), the near-opposite of the modern listless “apathy.” Do not confuse it with the positive equanimity (its near-namesake, with the opposite valence).