Socialism is a left-wing economic and political ideology that advocates for social ownership of the means of production—whether public, cooperative, or collective—rather than private ownership, and it comes in both market and non-market forms. Its modern roots trace back to 18th-century revolutionary movements, but it was solidified by Karl Marx and Friedrich Engels in the late 19th century, leading to a split by the early 1920s into the two dominant strands of communism and social democracy. While the Soviet Union became the first nominally socialist state, cementing an association with state-controlled economies, the term later shifted toward democratic socialism, which is distinct from social democracy's embrace of mixed economies, welfare states, and Keynesianism. After the revolutions of 1989, many socialist parties pivoted to "Third Way" politics, abandoning public ownership, yet socialism experienced a notable resurgence in the 2010s following the 2008 global financial crisis.