The phrase "major part" refers to a significant or important portion of something. It means that the specific component or element being described is a large or significant portion of the whole. Full definition
Dogs and cats have become major parts of millions of American families, and when summer brings hot weather and vacation travel, pets need special attention. (articles.orlandosentinel.com)
I constantly had to replace major parts in the car such as the radiator, spark plugs, fuel filter, etc.. (autolist.com)
This is as major part of the relationship for the young men involved in a sugar momma relationship. (seekingcougar.com)