Step 1: Key distinguishing idea:
Think of delegation as one link in a chain and decentralisation as the whole chain — delegation is the basic building block (superior to subordinate), and when it is repeated consistently at every level throughout the organisation, the result is called decentralisation.
Step 2: Practical illustration:
A branch manager delegating the task of daily cash reconciliation to a cashier is delegation. A company deciding that every branch manager, company-wide, will have full authority to sanction loans up to a limit without referring to head office is decentralisation.
Step 3: Degree of control retained:
In delegation, ultimate accountability always stays with the delegating superior; in decentralisation, while top management retains overall accountability, day-to-day decision-making power is genuinely dispersed.
Final Answer:
Delegation is a one-to-one transfer of authority for a task, compulsory in every organisation; decentralisation is the company-wide, optional spread of authority to build organisational capacity.