main is a noun referring to the dominant or primary feature, sense, or element of something. Main is often used to differentiate between a primary or important part to a lesser or unimportant part. It also refers to primary areas of activity, such as, 'She studied the main of American legal history.'
1. In the main, people who attended the party had a good time.
2. The main in the story followed different paths.
when used as a noun, main is usually preceded by an article ('the' or 'a').
main as an adjective means critical, important, or dominant. It is used to define a central element or concept of something.
1. I have the main points of the presentation.
2. The main idea of this paper is that poverty can lead to crime.
3. The main source of income for the family is from his job.
when used as an adjective, main is usually placed before the noun it describes.