Definition of I2C Communication Terms

In the I2C communication protocol, there are some specific terms that need to be understood. For example, "S" stands for the start signal, "Sr" stands for the repeated start signal, "SAD" is the address of the slave device, "W" and "R" stand for write and read operations respectively, "ACK" is the confirmation signal, "NACK" does not require confirmation signal, "RA" is the register address, "Data" is the valid data, and "P" is the stop bit.