The word "in mainstream" can be substituted with other terms that convey the same meaning. Some possible synonyms for "in mainstream" include "popular," "mainstream," "conventional," "fashionable," "trendy," "accepted," "orthodox," "dominant," and "established." These words help to describe something that is widely accepted, recognized, and approved by a large majority of people. They are often used to describe ideas, thoughts, or actions that are prevalent in a particular culture or society. Utilizing synonyms for "in mainstream" can help to provide clarity and variety in written or spoken language and enhance understanding.