# Derivation on-disk "ATerm" format

For historical reasons, [derivations](@docroot@/glossary.md#gloss-store-derivation) are stored on-disk in [ATerm](https://homepages.cwi.nl/~daybuild/daily-books/technology/aterm-guide/aterm-guide.html) format.

Derivations are serialised in the following format:

```
Derive(...)
```