Based on the number of parties, the following types of party system can be identified.
One Party System
This is one in which there is only one officially or constitutionally recognised political party in the state. No other political party is authorised by law to operate. Any opposition or rival party is seen as treason. This party automatically wins all elections because its candidates have no opposition. This party system is common to communist/fascist states such as the former Soviet Union, China, Egypt, Sierra-Leone, etc.
Two party System
This exist where there are two dominant political parties on the political scene. There may be other parties but these are small or relatively insignificant and can win very few seats in the legislature. Examples of countries operating two party systems are: United States of America, Britain and Nigeria during the Third Republic.
A Multi-Party System
A multi-party is one in which there exist more than two political parties of nearly equal strength and constitutional significance. An important factor responsible for the existence of several parties in a political system is the tendency in free politics for people to divide into several philosophy or special interest such as economic, cultural and religion. Example of countries practising multi-party system are Nigeria 1959-1966,1979-1983,1999 to date, Germany, Italy, etc.