投资学的英文：
investment
investment principles

investment是什么意思：
n. 投资（额）；投入；可投资的东西

invest material
覆盖材料

profits and losses on disposal of investments
转让投资的损益

He bought it purely as an investment.
他纯粹是作为投资而购买的。

Antiques are a very safe investment.
古玩是一种非常保险的投资对象。

Networking is an investment not a nuisance.
人际网络是一项投资而不是浪费。

principles是什么意思：
n. 原则，原理；起源；主义；道义

principle of discrimination
区别原则[指战时区别军事/非军事目标]

Adhesion to the principle of independence and abstract is infraction of the principle of honesty.
固守独立抽象原则是有悖于诚实信用原则的。

He was a man of the highest principles.
他是个道德崇高的人。

To instruct in a body of doctrine or principles.
传授以教条或信条的方式来教授、教导

The principle or law that orders the universe.
（佛教的）法约束天地万物的规则或法律