Mainstream describes ideas, activities, styles, or beliefs that most people in a society accept, follow, or consider normal. When something is mainstream, it's part of the common culture rather than unusual or specialized.

Mainstream movies play in regular theaters and appeal to wide audiences, while independent or art films might attract smaller, more specific groups. Mainstream news sources report stories that interest most people, while niche publications focus on particular topics like rare coin collecting or competitive robotics.

The word suggests the main current of a river: most of society flows in this direction. If you wear mainstream clothing, you're dressing like many others your age. If you listen to mainstream music, you're enjoying songs that dominate the radio and streaming charts.

Something can enter the mainstream when it moves from being unusual to widely accepted. Skateboarding was once considered rebellious and fringe, but it became mainstream and is now an Olympic sport. Personal computers were specialized tools for hobbyists in the 1970s before becoming mainstream in homes and schools.

The opposite of mainstream might be alternative, underground, or niche. These aren't value judgments: mainstream simply means widely shared and accepted, while other things appeal to smaller, more specialized audiences. Both mainstream and non-mainstream things have their place.

As a noun, the mainstream is the group of people, ideas, or culture that most of society follows.