Which resistor rating is specified as a given fraction per degree Celsius?

The temperature coefficient specifies exactly how much a component's resistance will drift for every single degree Celsius change in ambient temperature. It is typically expressed in parts per million per degree Celsius (ppm/°C) or simply as a given fraction per degree. The other ratings measure completely different parameters: power rating defines the maximum heat dissipation in watts, tolerance defines the manufacturing precision as a percentage, and the Ohmic value is the base resistance. Only the temperature coefficient links a component's resistance drift directly to changes in temperature.