The present application relates to a lighting device and in particular to a lamp, a transition member for mounting a lamp, a lamp body and a junction box assembly, by which problems such as inconvenient operation and low efficiency in connecting wires during the mounting of a lamp can be solved. The lamp provided by the present application comprises a lamp body and a transition member which is configured to mount the lamp body in a mounting position. The transition member comprises a mounting portion and a placement portion; the mounting portion is configured to be mounted in said mounting position; and the placement portion enables the lamp body to be placed thereon before the mounting is completed, and in this state, wires connected between the lamp body and the mounting position are not shielded so that it is possible to connect the wires.