In European football, the terms "hooligans" and "ultras" conjure up images of the darker side of the game: violence, fans clashing outside stadiums and far-right supporter groups in Italy.
But in Major League Soccer in the US, fans are giving the terms a new more family-friendly meaning.
Giles Gibson went along to watch DC United versus LA Galaxy in the US capital, Washington, to find out more:
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UPSOT Fans celebrating
DC United's diehard fans are there week in, week out, to cheer on their team
Just like in Europe, supporters groups like the District Ultras sit together in the same stand every week.
Tim Sheetz is a member of the Ultras and says they've brought over one crucial piece of traditional football fan culture: undying loyalty to their club
Byte: Tim Sheetz, District Ultras
"What we were trying to create was what the Ultras of Europe and the Barras of South America are trying to do: 90 minutes of non-stop support."
But right alongside and even amongst these hardcore fans, families and children have also come for a day out
And although families will always make up a big part of the crowd, local journalists say peaceful supporters groups like the Ultras are key to the MLS and its future growth
Steven Goff is a soccer writer for the Washington Post
Byte Steven Goff
Strapline: Steven Goff, football writer for The Washington Post
"I think you're seeing a greater connection now between the supporters and the clubs. There's a greater percentage now of people who come to the games who live and die with these teams now."
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MLS still has a long way to go until it can mimic the success of the big American sports like basketball,
Or even the European football leagues themselves.
But its fan culture is a truly unique mix.
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