Introduction:
Formal and informal organizations are two different types of organizational structures that coexist and complement each other in achieving the goals of an organization. While formal organizations are created deliberately with a defined structure and hierarchy, informal organizations emerge naturally based on social interactions within the formal structure.

Complementary Nature:
Formal and informal organizations are complementary to each other as they serve different purposes and fulfill distinct needs within an organization. Let's understand how they complement each other:

1. Formal Organization:
- Defined Structure: Formal organizations have a predefined structure with clear roles, responsibilities, and reporting relationships. This structure ensures smooth functioning, coordination, and accountability.
- Efficient Communication: Formal organizations establish formal channels of communication, such as memos, emails, meetings, etc., to ensure effective and timely flow of information.
- Goal-oriented: Formal organizations are designed to achieve specific objectives and goals. They provide guidelines and procedures to enhance efficiency and productivity.
- Legal Framework: Formal organizations operate within a legal framework and are bound by rules and regulations. They ensure compliance with legal and ethical standards.

2. Informal Organization:
- Social Relationships: Informal organizations are based on personal relationships, common interests, and social interactions among employees. They develop naturally and are not formally established.
- Flexibility and Adaptability: Informal organizations are flexible and can adapt quickly to changes in the formal structure. They provide support and facilitate communication among employees.
- Employee Satisfaction: Informal organizations fulfill the social and emotional needs of employees, fostering a sense of belonging, trust, and mutual support.
- Information Sharing: Informal organizations facilitate the sharing of tacit knowledge, experiences, and expertise that may not be formally documented.

Complementary Roles:
- Formal organizations provide a framework for planning, organizing, and controlling processes, while informal organizations contribute to the social and psychological well-being of employees.
- Formal organizations establish authority, set goals, and allocate resources, while informal organizations provide a platform for networking, mentoring, and informal learning.
- Formal organizations ensure compliance with rules and regulations, while informal organizations promote teamwork, collaboration, and innovation.

Conclusion:
Formal and informal organizations are two sides of the same coin, working together to achieve organizational objectives. While the formal structure provides stability, control, and efficiency, the informal structure fosters employee satisfaction, creativity, and adaptability. Recognizing and harnessing the strengths of both structures can lead to a harmonious and successful organization.