Rationalism in architecture emphasizes logical, functional, and mathematically ordered design, separating it from ornate styles like baroque and art nouveau. The movement has roots in ancient Greece and evolved through the Enlightenment and 20th-century practices, focusing on basic geometric forms and modern materials such as concrete. Notable architects like Mies van der Rohe and Le Corbusier were instrumental in developing these principles, leading to new building types that prioritize simplicity and urbanism.