Commission:

Commission is defined as extra income generated by the person like a employee commission is based on the net sale or extra generated sale.

Contingent liability:

A contingent liability is a part of liability, It is a type of liability which may arise, it is uncertain. There are many types of contingent liability like Law case, A change in govt. policy, Product warranty, etc.

Expense:

For generating the revenue the cost of the operation which expired with in the year is called expense.

Example: Rent expense, advertisement expense.