A first terminal apparatus is provided in a communication system that includes a plurality of terminal apparatuses configured to perform sidelink communication via a PC5 interface, and a network including a base station apparatus, the plurality of terminal apparatuses including the first terminal apparatus and a second terminal apparatus. The second terminal apparatus is a terminal apparatus capable of relay between the first terminal apparatus and the network, or a relay terminal apparatus that performs relay between the first terminal apparatus and the network. The first terminal apparatus is configured to receive, from the base station apparatus, a configuration for measurement in the sidelink communication, and perform measurement in the sidelink communication from the second terminal apparatus, using the configuration.