Human activity recognitionHuman Activity Recognition (HAR) is a specialized tool applied in health care and many such time-critical, real-life applications mainly for monitoring purposes. In health care, HAR is applied for health monitoringHealth monitoring, health condition detection, disease monitoringDisease monitoring, disease predictionDisease prediction, disease identification, progress monitoring in rehabilitation process, etc. In smart surveillance system, HAR would aid in identifying the posturePosture or activity of a person or human being in a restricted area or sensitive area at a particular time and accordingly could be detected as normal or abnormal or alarming based on previously defined guidelines. Now, with minimum infrastructural requirements, real-time data gathering and analysis and alert generation if necessary, support of enabling technologiesEnabling technologies are required. Fundamental concepts of such advanced tools and technologies such as sensors, Internet of thingsInternet of Things (IoT) (IoT), machine learningMachine Learning (ML) (ML), deep learningDeep Learning (DL) (DL), and cloudCloud technologies are being briefly described over here to understand the ecosystem of HARHuman Activity Recognition (HAR) and HAR-related applications (Thakur and Biswas in J. Ambient Intell. Humaniz. Comput. 11:5433–5444, 2020 [1]).