► mainlyas the largest or most important reason, thing, part of something, etc.: Our customers are mainly young people. I joined the club mainly because it has a swimming pool.
► mostly used to say that something is true about most situations or about most people or things: We went hiking one morning, but mostly we just relaxed on the beach.
► chiefly chiefly means the same as mainly, but sounds more formal and is used especially in writing: The forest consists chiefly of fir trees.
► principally firstly and most importantly and as the largest part: Foreign aid was sent principally to the south of the region.
► largely mainly, but not all. Largely is a little more formal than mainly or mostly: The car industry is largely concentrated in two areas of the country.
► primarily mainly because of one reason or situation, which is more important than any other: The animal is endangered primarily because of the loss of habitat.
► essentially used to give the main and most basic facts about something: The suicide rates have remained essentially the same over the past ten years.
► predominantly mainly, most commonly, or most noticeably: She is Hispanic, but she grew up in a predominantly white neighborhood.