Is it farther or further?
combining form used in forming the names of devices for stabilizing or regulating (thermostat, etc.), from Greek statos "standing, stationary," from histanai "to cause to stand," from PIE root *sta- "to stand" (see stet). First used in heliostat "an instrument for causing the sun to appear stationary" (1742).
Something that stabilizes: barostat.
Something that inhibits: hemostat.