Party coalition is common in a

A party coalition occurs when two or more political parties come together to form a government or to pursue shared political objectives. This is most commonly found in a multi-party system.

In a multi-party system, several political parties compete for power, and it is common for no single party to win an outright majority of seats in the legislature. When this happens, parties must negotiate and form coalitions to achieve a working majority. This coalition-building is a defining feature of multi-party democracies.

Coalitions are not characteristic of other party systems:

• In a one-party system, only one political party is legally permitted to hold power, so there is no partner to form a coalition with.
• In a two-party system, one of the two major parties typically wins enough seats to govern alone, making coalitions rare.
• A "zero party system" describes a state with no political parties at all, so coalitions are impossible.

Countries like Israel, India, and Germany frequently demonstrate coalition politics because their multi-party systems make it difficult for any single party to secure a parliamentary majority on its own.