Answer:
A single party system is where a single party has all the power and no opposition or any other party exists. This system is in china where communist party of china is the only party and competition is within the party to select president, prime minister or any other important posts. This is no where close to democracy and people's will is not the supreme.
In a multiparty system, the number of parties is unlimited. Anyone can establish a party if he meets necessary conditions. This is a true of democracy