The things description is a tool to realise the representation of physical things as virtual things of the information world to facilitate automatization, interoperability and composability for IoT applications. Things description specifies a general way for how to map physical things in the physical world to virtual things in the information world in order to enable things of the IoT to be effectively discovered, interpreted and used. The goal of this Recommendation is to specify requirements for an effective way of representing things as far as possible in a homogeneous way. The focus of the document is on the following two concerns of things description. " Representing physical things as virtual things to map the physical things into information world; " Representing the relationship of virtual things to reflect the relationship of the represented physical things The corresponding requirements of things description in the IoT are specified, including: " High level requirements of things description in IoT " Requirements on the characterization aspects of things description in IoT This Recommendation may be relevant for the matters addressed by ITU-T Y.4114 "Specific requirements and capabilities of the Internet of things for big data", e.g. semantic related data processing.