The Kohn-Lebowitz theorem is a result in statistical mechanics that addresses the behavior of systems in equilibrium. It provides a mathematical framework for understanding how macroscopic properties emerge from microscopic interactions among particles. This theorem is particularly useful in studying phase transitions and critical phenomena. Developed by Kohn and Lebowitz, the theorem emphasizes the importance of correlation functions in describing the state of a system. It helps researchers analyze how local interactions can lead to global behaviors, making it a key concept in both theoretical and applied physics.