This thermistor belongs to a negative temperature coefficient thermistor. MF72 is the model of the thermistor, 5D9 is the specification of the thermistor, the number in front of D indicates the size of the thermistor chip in mm, and the number after D indicates the nominal resistance value of the thermistor in ohms. A thermistor is used to suppress inrush current. Generally speaking, the larger the size and the smaller the nominal resistance value, the greater the steady-state current value that the product can withstand.
This thermistor is a negative temperature coefficient thermistor.