There is provided a terminal device which communicates with a base station apparatus. The terminal device includes a reception unit that decodes a downlink control channel (PDCCH) or an enhanced downlink control channel (EPDCCH) including a downlink control information (DCI) format. A field of a downlink assignment index (DAI) is provided in the DCI format for a TDD operation, in a case of a time division duplex (TDD) primary cell. The field of the DAI is not provided in the DCI format for the TDD operation, in a case of a frequency division duplex (FDD) primary cell.