principal / principle
principal: adjective meaning 'the most important'
principal：形容词，意思是“最重要的”
Examples:
例句：
The principal reason for my decision was the money.
What are the principal irregular verbs?
我做决定时最看重的就是钱。
最重要的不规则动词有哪些？
principle: a rule (usually in science but also concerning morals)
principle：定律、原则（通常用在科学领域，不过也用在相关的道德领域）
Examples:
例句：
It's the first principle of aerodynamics.
He has very loose principles.
这是热力学第一定律。
他的原则弹性很大。
