Digital twins (DT) have recently gained significant interest among architecture, engineering, construction, and operations (AECO) industry professionals and researchers. However, there is no consensus on the definition of digital twins to the point that some practitioners use building information models (BIM) and digital twins synonymously. This research focuses on developing a scope definition for the identification and classification of DT use cases. The results will help researchers and industry practitioners with planning the implementation of operational digital twins. A detailed review of the literature was conducted to find the existing definitions of operational digital twins. Afterward, an extensive review of use cases of operational digital twins was completed. Furthermore, these use cases were defined through a categorical content analysis, and they were placed within an existing widely used ontology. Examples of operational DT use cases include remote asset monitoring, remote asset control, and asset performance prediction. Use cases identified in this paper were reviewed by leading experts in the DT community. The findings of this paper will benefit researchers and industry practitioners in planning for digital twin implementations by providing a common language with attributes to define specific DT use cases.