Introduction:
The informal loan sector includes various agencies that provide loans outside the traditional banking system. These agencies cater to individuals who may not have access to formal banking services or who prefer borrowing from non-institutional sources. However, one agency that is not included in the informal loan sector is the bank.

Explanation:
Here, we will discuss each option and explain why it is or isn't a part of the informal loan sector:

a) Bank:
Banks are formal financial institutions that provide loans and other financial services to individuals and businesses. They operate within a regulatory framework and are required to follow specific guidelines and lending practices. Banks are not a part of the informal loan sector as they are regulated and have well-defined processes for loan disbursal, repayment, and interest rates.

b) Village money lender:
Village money lenders are often a significant part of the informal loan sector. They are individuals or groups within rural communities who lend money to borrowers at higher interest rates compared to banks. They do not operate under any regulatory framework and often rely on personal relationships and trust. Village money lenders cater to individuals who may not have access to formal financial institutions or who require quick and easy loans.

c) Trader:
Traders, also known as merchant money lenders, are a part of the informal loan sector. They are individuals or businesses who provide loans to individuals based on their trade or business activities. Traders often lend money to other traders or individuals involved in similar business activities. They operate outside the formal banking system and may charge higher interest rates compared to banks.

d) Relative of borrower:
Relatives of borrowers are not considered as a part of the informal loan sector. When individuals borrow money from their relatives, it is usually based on personal relationships and trust, rather than formal lending processes. Relatives may lend money without charging any interest or may charge a minimal interest rate. However, this type of borrowing does not fall under the purview of the informal loan sector.

Conclusion:
In conclusion, the agency that is not included in the informal loan sector is the bank. Banks operate within a regulated framework and follow specific lending practices, making them a part of the formal financial system. On the other hand, village money lenders, traders, and borrowing from relatives are all part of the informal loan sector, providing loans outside the traditional banking system.