Niklas Luhmann's theory of social systems identifies three key types of communication media that facilitate interaction within different subsystems of society: money, truth, and power. Each of these media serves to reduce complexity and stabilize expectations within its respective system. Here is a description of each:

### 1. Money (Economic System)

Function: Money serves as a medium of communication within the economic system. It facilitates the exchange of goods and services by providing a standardized measure of value.

Key Characteristics:
- Standardization: Money provides a common reference point for value, simplifying transactions and enabling the comparison of diverse goods and services.
- Trust and Credit: The use of money relies on collective trust in its stability and acceptability, as well as in the institutions that manage it.
- Temporal Flexibility: Money allows for saving, investing, and borrowing, coordinating economic activities over time.
- Decoupling of Transactions: It separates transactions in time and space, allowing for more flexible economic interactions.

Impact: Money reduces the complexity of economic exchanges, making trade more efficient and predictable. It also facilitates the functional differentiation of the economic system by providing a unique medium for economic communication.

### 2. Truth (Scientific System)

Function: Truth acts as a medium of communication within the scientific system. It enables the validation and dissemination of knowledge, guiding scientific inquiry and research.

Key Characteristics:
- Empirical Validation: Truth is established through empirical evidence and logical reasoning, forming the basis for scientific claims and theories.
- Consensus and Peer Review: Scientific truth is maintained through consensus within the scientific community and rigorous peer review processes.
- Objective Standards: Truth in science relies on objective standards and methodologies that ensure consistency and reliability in research findings.

Impact: Truth reduces the complexity of knowledge by providing a reliable framework for understanding the world. It stabilizes expectations within the scientific community and supports the accumulation of reliable knowledge over time.

### 3. Power (Political System)

Function: Power serves as a medium of communication within the political system. It enables the coordination and control of social actions and decisions, facilitating governance and policy implementation.

Key Characteristics:
- Authority and Legitimacy: Power is exercised through institutions and individuals who hold authority and legitimacy within the political system.
- Decision-Making: Power structures enable the making and enforcement of decisions that affect the society at large.
- Coercion and Compliance: Power often involves mechanisms of coercion to ensure compliance with laws and regulations.

Impact: Power reduces the complexity of social order by providing mechanisms for governance and control. It stabilizes societal expectations by ensuring predictable and enforceable rules and decisions, thus maintaining social cohesion and order.

### Summary

In Luhmann's theory, these three communication media—money, truth, and power—are essential for the functioning of their respective social systems. Each medium reduces complexity and stabilizes interactions within its domain, ensuring the smooth operation and differentiation of economic, scientific, and political systems.