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. Restoring control to primary controller. 恢复主控制器的控制。
2. Received command to return control to primary controller. 已收到恢复主控制器控制的命令。
3. Low birth weight infant is a primary commonality health problem in the world. 低出生体质量儿是世界上一个主要的公共健康问题。
英英解释
n.
1. a preliminary election where delegates or nominees are chosen
2. one of the main flight feathers projecting along the outer edge of a bird's wing
3. coil forming the part of an electrical circuit such that changing current in it induces a current in adj.
1. of first rank or importance or value; direct and immediate rather than secondhand
2. not derived from or reducible to something else; basic
3. most important element
4. of or being the essential or basic part
5. of primary importance
