Picture a hospital, a school and a bus route, and then ask the plain question: who pays, and who decides? Social democracy is one answer to that pair of questions. Taxes pay, so that everyone can use the things, and elections decide, so nobody takes that power for granted. Hold both halves at once and the word opens up. Said of a set of ideas it is that answer itself; said of a place it is a country that has given that answer, which is why the grammar turns countable the moment you point at one.
The name is its own two halves: social, the aim of looking after everyone, and democracy, the rule that it has to be done through elections.
名字本身就是兩半：social 是「照顧到所有人」的目標，democracy 是「必須靠選舉來做」的規矩。
transparent compound of social + democracy; supported by the LDOCE definition in the packet ('some ideas of socialism combined with democratic principles')
One branch
一套想法，和照這套想法運作的國家
兩個意思是同一組回答的兩種指法：一個指想法本身，一個指採用這組回答的地方。
noun · C1
A political and economic system that tries to reach socialist aims, such as sharing wealth more evenly and paying for services like health care and schools for everyone, while keeping free elections and personal freedom.
社會民主（主義）