Solid waste is a heterogeneous mixture of discarded materials generated from households, commercial establishments, industries, institutions, construction activities, agriculture, and municipal services. Understanding its physical and chemical characteristics is essential for designing efficient collection, transportation, treatment, recycling, and disposal systems in smart cities. Proper characterization helps improve resource recovery, reduce environmental pollution, and support sustainable waste management practices. The physical characteristics of solid waste determine how it behaves during storage, handling, transportation, processing, and disposal. One of the most important physical characteristics is composition. Municipal solid waste typically contains biodegradable organic matter, paper, cardboard, plastics, glass, metals, textiles, rubber, leather, wood, electronic waste, and inert materials such as dust and construction debris. The proportion of these components varies depending on the level of urbanization, income, lifestyle, and seasonal changes. Density is another significant physical property. It refers to the mass of waste per unit volume and influences the design of storage bins, collection vehicles, transfer stations, and landfill capacity. Freshly generated waste generally has lower density, while compacted waste has higher density, enabling more efficient