---
title: "About"
description: "What aontu defines, who maintains it, and how the TypeScript and Go implementations are tested."
source: "https://aontu.dev/about/"
---

# About

aontu is an open source language for defining a software system: what it contains, what those things must be, and how they may relate. It is an engine you install and run yourself, and this site is its documentation.

## What it is

aontu defines a system's entities, their types, and the relations between them. Types, defaults, and data use the same notation and combine through [unification](https://aontu.dev/docs/unification). The engine reports a conflict when statements cannot agree.

Use a definition to check a proposed change before accepting it. The result includes a verdict, error codes, and source locations that a program can act on. Read [why aontu](https://aontu.dev/why) for the design rationale, or try the [playground](https://aontu.dev/playground).

## The name

**aontu** is from the Irish for agreement, union, consent: two things made one. It is pronounced roughly "AYN-too", and it is written lowercase everywhere, because it is the command you type. The project is named for what the engine does rather than for what it is built from.

## Two implementations, held together

aontu ships as a TypeScript package on [npm](https://www.npmjs.com/package/aontu) and as a Go module at `github.com/aontu-lang/aontu/go`. TypeScript is the canonical implementation. Both implementations run the same language-neutral test corpus, and both require 100% test coverage with documented exclusions.

Authored examples and the playground run `aontu@0.72.0`. Documentation is imported from the engine repository, where examples are tested against that checkout. Those pages can describe changes ahead of the installed package. [/versions.json](https://aontu.dev/versions.json) reports the website's version information.

## Who maintains it

aontu is written and maintained by [Richard Rodger](https://richardrodger.com). It is MIT licensed. Contributions, bug reports and corrections are welcome through the issue tracker; see [contact](https://aontu.dev/contact).

## Source and machine-readable content

[The engine](https://github.com/aontu-lang/aontu)

Both implementations, the shared corpus, and the documentation these pages are generated from.

[This site](https://github.com/aontu-lang/web)

The Astro source for aontu.dev. Versioned and deployed separately from the engine.

[/llms.txt](https://aontu.dev/llms.txt), [/openapi.json](https://aontu.dev/openapi.json), [/errors.json](https://aontu.dev/errors.json)

The machine-readable index, the description of this site's content API, and every error code the engine can raise. The [grammar](https://aontu.dev/grammar/aontu.gbnf) is published too, for constrained decoding.

Next: the [tutorial](https://aontu.dev/docs/tutorial) starts from nothing, and the [playground](https://aontu.dev/playground) runs the engine in your browser.