chief 拽人时，表同类中职位最高，权力最大；指物时，表同类中最重要，价值最高。
principal 用于人时，指地位优于其他人；用于物时，指该物在大小、重要性等方面优于他物。
main 通常只用于物。指在一定范围内，某物的重要性、体积或力量等超过其它物。
major 指同其他人或其它物、问题等相比较，显得更加重要和突出。
leading 侧重指具有影响力或凝聚力。从而有主导和引导的作用。
capital 着重指因重要性、意义、优越或重大而名列同类之首。
foremost 侧重指在行进或发展过程中居首位。
primary 通常不用于人。用于物时，指在重要性方面占第一位。
参考例句
1. Fish eggs and meat are all major sources of protein. 鱼类鸡蛋和肉类都是重要的蛋白质来源。
2. Programme of major component repair or replacement during the project life. 在项目生命期内，主要部件修复或置换的计划；
3. The introduction should start with what you do in this paper, the major contribution. 引言的开始，要讨论你在这篇论文做了什么，你的主要贡献。
英英解释
n.
1. a commissioned military officer in the United States Army or Air Force or Marines; below lieutenant
2. British statesman who was prime minister from 1990 until 1997 (born in 1943)
3. a university student who is studying a particular field as the principal subject
4. the principal field of study of a student at a university v.
1. have as one's principal field of study
2. of greater importance or stature or rank
3. greater in scope or effect
4. greater in number or size or amount
5. of the field of academic study in which one concentrates or specializes
6. of a scale or mode
7. of greater seriousness or danger
8. of full legal age
9. of the elder of two boys with the same family name
