This document discusses political systems from both an institutional and systemic perspective. It defines a political system as a structural and functional organization consisting of interdependent parts that form an integrated whole to achieve objectives. A political system exists within a social system and interacts with its external environment. The document outlines David Easton's model of a political system, which consists of inputs, a conversion process, outputs, and feedback between the system and its environment. It also discusses different types of modern political systems based on principles of democracy and modernity.