Collapse: The collapse refers to a sudden breakdown or failure of a system or structure. In this case, it could refer to the collapse of the Soviet Union due to various internal and external factors.
Transition: Transition denotes a process of change from one state or condition to another. After disbanding, the countries that were part of the Soviet Union went through a transition period as they established their independent governments.
Perestroika: Perestroika was an economic reform policy introduced in the late 1980s by Soviet leader Mikhail Gorbachev. It aimed at restructuring and revitalizing the economy but inadvertently contributed to political changes ultimately leading to disbandment.