What do subcultures often have in common with mainstream culture?
fashion

language

traditions

music

What subcultures and mainstream culture have in common is language and traditions.

Explanation:

Although every subculture has its own 'slang' (language that is restricted to a specific context or group of people) that characterizes its members, the language itself is the same as for those who belong to the 'Mainstream culture'. For example, Goths, Hippies or Hip Hop fans, they all share a particular way of speaking the same language as the ones in the mainstream culture. The same happens with traditions because they also belong to the society as a whole, though again, each subculture has its own special set of traditions.

Now, music and fashion are completely different from the mainstream culture. These two factors are propably the ones that most differentiate the subcultures from the others.