# Describe what is meant by a prefix in physics and explain why prefixes are useful when measuring physical quantities. Give two examples of prefixes to support your answer.

> Edexcel GCSE Physics (1PH0) — 1.1 Key concepts of physics · Describe · 4 marks

## Mark scheme (4 marks)

1. A prefix is a word or symbol placed before a unit that represents a power of ten multiplier (scaling factor).
2. Prefixes are useful because they avoid writing very large or very small numbers / make values easier to read and record.
3. Correct first example of a prefix with its symbol and multiplier, e.g. kilo (k) = × 10³, or mega (M) = × 10⁶, or milli (m) = × 10⁻³, or nano (n) = × 10⁻⁹, etc.
4. Correct second, different example of a prefix with its symbol and multiplier.

## Key terms

- [prefix](https://www.gradenine.co.uk/glossary/prefix)

## Related

- [Revision notes for Edexcel GCSE Physics (1PH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-what-is-meant-by-a-0ca58157) · Published by Druglandscape Ltd.