principle
/ˈprɪnsəpl/noun
1
- a fundamental truth or proposition that serves as the foundation for a system of belief or behaviour or for a chain of reasoning原理, 原则：
the basic principles of Christianity.
基督教基本教义。
1.1
- （一般作principles）a rule or belief governing one's personal behaviour（个人行为）准则; 规范：
struggling to be true to their own principles
为坚持他们自己的原则而奋斗
mass noun she resigned over a matter of principle.她因原则问题而辞职。
1.2
- mass noun morally correct behaviour and attitudes操守, 道义; 原则性; 正直：
a man of principle.
有原则的人。
1.3
- a general scientific theorem or law that has numerous special applications across a wide field原理; 定理; 基本原理。
1.4
- a natural law forming the basis for the construction or working of a machine（机器的）建构（或工作）原理：
these machines all operate on the same general principle.
这些机器总的工作原理都一样。
2
- a fundamental source or basis of something起源, 本原：
the first principle of all things was water.
水是万物之本。
2.1
- a fundamental quality or attribute determining the nature of something; an essence本质, 实质：
the combination of male and female principles.
男性与女性本性的结合。
2.2
- with adj. Chemistry an active or characteristic constituent of a substance, obtained by simple analysis or separation【化】成分, 要素：
the active principle of Spanish fly.
斑蝥制剂的活性成分。
USAGE
The words principle and principal are pronounced in the same way but they do not have the same meaning. Principle is normally used as a noun meaning 'a fundamental basis of a system of thought or belief'， as in this is one of the basic principles of democracy. Principal, on the other hand， is normally an adjective meaning 'main or most important'， as in one of the country's principal cities. Principal can also be a noun， where it is used to refer to the most senior or most important person in an organization or other group: the deputy principal. The spelling of principal when principle is meant， and of principle when principal is meant are quite common mistakes: around 5 per cent of citations for principle and principal on the British National Corpus represent one of these errors.
短语
in principle
1
- as a general idea or plan, although the details are not yet established or clear原则上：
the government agreed in principle to a peace plan that included a ceasefire.
政府原则上同意了一项包括停火在内的和平计划。
1.1
- used to indicate that although something is theoretically possible, in reality it may not actually happen在理论上, 据设想（实际上未必发生）：
in principle, the banks are entitled to withdraw these loans when necessary.
理论上, 银行在必要时有权收回这些贷款。
on principle
- because of or in order to demonstrate one's adherence to a particular belief根据行为准则, 按照原则：
he refused, on principle, to pay the fine.
他依据原则拒绝支付罚款。
词源
late Middle English: from Old French， from Latin principium 'source'， principia (plural) 'foundations'， from princeps, princip- 'first， chief'.