The paper introduces a new meta-generalized gradient approximation (meta-GGA) for density functional theory (DFT) called Strongly Constrained and Appropriately Normed (SCAN). SCAN is designed to satisfy all 17 known exact constraints on meta-GGAs and is also accurate for appropriate norms, including rare-gas atoms and nonbonded interactions. The authors construct SCAN by ensuring it satisfies rigorous bounds and exact constraints, such as the positivity of the exchange energy and the Lieb-Oxford bound for the exchange-correlation energy. They demonstrate that SCAN outperforms existing meta-GGAs like TPSS and revTPSS in terms of accuracy for various systems, including rare-gas atoms, weak interactions, and lattice constants. The functional is nonempirical and can be applied to a wide range of problems without empirical fitting. The paper also provides detailed formulas, figures, and tables for the construction and testing of SCAN, showing its superior performance in various benchmarks.The paper introduces a new meta-generalized gradient approximation (meta-GGA) for density functional theory (DFT) called Strongly Constrained and Appropriately Normed (SCAN). SCAN is designed to satisfy all 17 known exact constraints on meta-GGAs and is also accurate for appropriate norms, including rare-gas atoms and nonbonded interactions. The authors construct SCAN by ensuring it satisfies rigorous bounds and exact constraints, such as the positivity of the exchange energy and the Lieb-Oxford bound for the exchange-correlation energy. They demonstrate that SCAN outperforms existing meta-GGAs like TPSS and revTPSS in terms of accuracy for various systems, including rare-gas atoms, weak interactions, and lattice constants. The functional is nonempirical and can be applied to a wide range of problems without empirical fitting. The paper also provides detailed formulas, figures, and tables for the construction and testing of SCAN, showing its superior performance in various benchmarks.