Laws, Theories, and Principles
A scientific law describes a repeated pattern, a theory explains why or how a pattern occurs, and a principle is a broad guiding idea used across situations.
Practice This ConceptMain explanation
Teacher explanation
Students often think theory means a weak guess, but in science a theory is an evidence-based explanation. A law usually tells what happens under certain conditions, often in a concise statement or equation. A principle may guide reasoning in many connected cases. These ideas can be revised if strong new evidence demands it.
Example
A law may describe how force and acceleration are related, while a theory may explain a broader set of observations using deeper ideas.
Simple analogy
Law says what; theory says why.
Common confusion
A common mistake is saying that a theory becomes a law after proof. Laws and theories do different jobs; one does not simply graduate into the other.
Exam tip
When asked to compare, write law as pattern, theory as explanation, and principle as broad guiding rule.
Answer writing and exam use
1-mark use
Write the exact meaning of laws, theories, and principles in one clean line.
2-mark use
Define laws, theories, and principles and add one example or condition.
3-mark use
Explain laws, theories, and principles, show the method or example, and mention the common mistake.
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