The rowheader role - ARIA Reference Guide

Composites
Represent containers for navigating interactive descendants.
Landmarks
Represent top-level sections of a page, relevant to a specific purpose, that a user may want to scan for quickly and could appear in a site map or table of contents.
Live Regions
Represent dynamic content or announcements, typically updated as a result of an external event when user focus may be elsewhere.
Structures
Represent non-interactive parts of a page that organize content into coherent units.
Widgets
Represent focusable, interactive elements.
Windows
Represent inner windows that are children of the main web document.

WAI-ARIA spec HTML-ARIA spec

Structure(opens in new window)Widget(opens in new window)Required Context(opens in new window)

Description

A cell containing header information for a row.

Note

*May be interactive or non-interactive depending on the context: Interactive when inside a grid or treegrid.

Allowed Content

Flow content but with no main element descendants.

Required Context Roles

row

HTML Elements with Implicit ARIA Role

th[scope=row]

Allowed HTML Elements

th
th[scope=row] (role attribute unnecessary)
div, span, p, other elements that can receive any role