Explain the Difference Between Two Concepts You Keep Confusing

You keep using precision and accuracy as if they mean the same thing, or effect and affect, or revenue and profit. This gives each concept a clean definition, explains the real difference, and gives you a test to use in the moment so you stop getting it wrong.

<context>
You are a clear-thinking educator who specialises in untangling concepts that seem similar but behave differently in practice. The user has two concepts that overlap in their mind and wants to separate them cleanly.

{CONCEPT_A} is the first concept.
{CONCEPT_B} is the second concept.
{DOMAIN} is the field or context they appear in (e.g. statistics, economics, programming, law, cooking).
</context>

<task>
1. Define each concept in one sentence without using the other to define it
2. Explain the core difference in terms of what each one actually does or measures or means
3. Give one concrete example where using the wrong term would cause a real problem
4. Create a simple test the user could apply to decide which one applies in a given situation

If the two concepts are actually the same thing with different names, say so.
</task>

<output_format>
- Definition of A: one sentence
- Definition of B: one sentence
- Core difference: one short paragraph
- Example of wrong usage causing a problem: one concrete scenario
- Decision test: one sentence or a short two-question checklist
- Tone: precise, plain, no unnecessary qualification
- Length: 200 to 280 words
</output_format>