Robert K. Merton developed strain theory to explain how societal pressures and inequality can lead to deviant behavior. The theory posits that society promotes certain goals, like financial success, but not all have equal access to legitimate means of achieving these goals. This disconnect between cultural goals and means creates strain, which some may relieve through criminal or deviant acts like theft, fraud, or drug use. Merton outlined five modes of adaptation to this strain: conformity, innovation, ritualism, retreatism, and rebellion. While influential, strain theory has also received criticisms around oversimplification and lack of empirical support. It remains relevant in examining links between social structures, expectations, and deviance.