A terminal device transmits a signal to a base station apparatus through uplink. The terminal device considers a priority level for multiple MAC control elements in the logical channel prioritization procedure for the uplink, in a case where initial transmission is performed. At least first and second MAC control elements are included in the multiple MAC control elements. The first MAC control element provides the base station apparatus with information on an amount of first data available for transmission within a first buffer for the uplink. The second MAC control element provides the base station apparatus with information on amount of second data available for transmission within a second buffer for a first link that is used for communication between the terminal device and a different terminal device. The first MAC control element has a higher priority level than the second MAC control element except when being included for padding.