Explain the Difference Between a Federal and a Unitary Constitution

Under a unitary constitution, such as the United Kingdom's, decision-making power is centralised in one authority, such as the Westminster parliament. Under a federal constitution, such as the United States', quasi-autonomous states are delegated substantial powers to resolve issues in their own ways, with the central government exercising relatively limited power, usually over areas such as defense and macroeconomics. In recent years the unitary nature of the constitution of the United Kingdom has been undermined by a process known as devolution, in which decision-making power has been delegated to assembles in Northern Ireland and Wales, and a national parliament in Scotland. However, the constitution retains its essential unitary nature by virtue of the fact that the Westminster parliament has the power to abolish or restrict the competencies of these bodies at any time; the United States federal government has no such explicit power.