Arduino Uno ADC voltage, is it Vpp or Vrms?

For the arduino Uno the adc has a rating of 0 to 5V. So if i am inputting an AC signal, should the signal be in the range of 0 to 5V Vpp or 0 to 5V Vrms (considering an ideal cosine wave).

It should be 0 to 5V Vpp.

This should not be in the installation part of the forum it is a project or circuit matter.