# principle

/ˈpɹɪnsəpəɫ/ (US) · /pɹˈɪnsɪpəl/ (UK)

Source: https://englishreference.com/word/principle
Updated: 2026-08-15

## Senses

### 1. moral belief

noun · CEFR B2

a moral rule or belief that helps you know what is right and influences your behavior.

For teachers: a fundamental truth or proposition that serves as the foundation for a system of belief or behavior or for a chain of reasoning.

- She refused to lie about the accident because it went against her principles.
- The senator maintained that sticking to his principles was more important than winning the upcoming election through compromise.

### 2. scientific law

noun · CEFR B2 · Academic · Technical

a basic law of nature or a rule that explains how a machine or system works.

For teachers: a fundamental law, axiom, or doctrine of nature or science.

- The pilot explained the basic principles of flight to the passengers.
- Archimedes' principle explains why ships float by calculating the upward force exerted by the displaced water.

### 3. general rule

noun · CEFR B2 · Academic

a general idea or rule that is used as a base for other ideas.

For teachers: a general scientific theorem or law that has numerous special applications across a field.

- In principle, the plan sounds good, but we need to see the costs.
- While the two parties agree on the proposal in principle, they remain divided on the specific details of implementation.

### 4. active ingredient

noun · CEFR C2 · Technical · Formal

a basic substance in a plant or medicine that gives it a special quality.

For teachers: a constituent of a substance, especially one giving it a particular quality or effect.

- Scientists isolated the active principle in the leaf that helps reduce pain.
- The laboratory succeeded in extracting the bitter principle from the root, allowing for more precise pharmaceutical testing.

Usage: Often used in chemistry or pharmacology to describe the 'active principle' of a drug.

## Examples

- The basic principle of the machine is very simple.
- The company operates on the principle that happy employees are more productive and creative.
- While the mathematical principles underlying the theory are sound, the practical application remains difficult due to the extreme environmental conditions required for the experiment.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.