> ## Documentation Index
> Fetch the complete documentation index at: https://hexagraph-docs.voyla.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Fields Overview

> Overview of Hexagraph's registry of academic research fields.

Fields are the second level of the Hexagraph topic hierarchy. There are 26 fields spread across 4 domains. Each field contains multiple subfields.

The topic hierarchy is: Domain → **Field** → Subfield → Topic

## Filter and sort fields

The API supports filtering and sorting on fields. See [Filtering](/guides/filtering) and [Sorting](/guides/sort) for syntax.

| Field            | Sort | Filter |
| ---------------- | :--: | :----: |
| `cited_by_count` |   ✓  |    ✓   |
| `name`           |   ✓  |        |
| `domain.id`      |   ✓  |    ✓   |
| `id`             |   ✓  |    ✓   |
| `outputs_count`  |   ✓  |    ✓   |