> For the complete documentation index, see [llms.txt](https://ourresearch.gitbook.io/help.openalex.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ourresearch.gitbook.io/help.openalex.org/how-it-works/concepts.md).

# Concepts

{% hint style="warning" %}
These are the original OpenAlex Concepts, which are being deprecated in favor of [Topics](/help.openalex.org/how-it-works/topics.md). We will continue to provide these Concepts for Works, but we will not be actively maintaining, updating, or providing support for these concepts. Unless you have a good reason to be relying on them, we encourage you to look into [Topics](/help.openalex.org/how-it-works/topics.md) instead.
{% endhint %}

Our legacy Concepts uses a system adapted from MAG to assign multiple concepts to works using their titles and abstracts. You can learn more about these concepts and how they are assigned [in our technical documentation here.](https://docs.openalex.org/api-entities/concepts)