1. The two imaginary lines around the Earth at approximately 23.5 degrees north and 23.5 degrees south of the equator?.
2. Each of two corresponding circles on the celestial sphere where the sun appears to turn after reaching its greatest declination, marking the northern and southern limits of the ecliptic.
3. Etymology: from Middle English tropik, from Old French tropique, from Late Latin tropicus, from Latin, tropicus, "pertaining to a turn", from Greek tropikos, "of or pertaining to a turn" or "change of a turn".