The 8 Content Parts of HTML

A Content Part associates a set of Content Mixes to a Topic Block

When the Topic Block is a Heading Block, the Content Part is specifically a Content Section. Otherwise, when it's a Title Block, the Content Part is a respective Content Segment.

Since a Title Block do not create a document outline, a Content Segment belongs to a parent Content Section. So: each Content Section, and the set of Header and Footer Parts they initiate, is a division of a Content Window or another Content Section.

Cell Segment

A Cell Segment bound contents for a row under a Column Title in a Tabular Layer

The syntax is a td element with the following attributes and child elements:

<td></td>

Association Segment

An Association Segment bound contents describing an Association Title in an Description Layer

The syntax is a dd element with the following attributes and child elements:

<dd></dd>

Details Segment

A Details Segment bounds a Details Title and its contents.

The syntax is a details element with the following attributes and child elements:

<details>
  <summary>[title]</summary>

</details>

Fieldset Segment

A Fieldset Segment bounds a Fieldset Title and its contents

The syntax is a fieldset element with the following attributes and child elements:

<fieldset>

</fieldset>

General Section

A General Section bounds an Heading Block and its contents

It becomes a Region Landmark if it has an accessible name via one of the following attributes: aria-label, aria-labelledby, and title.

The syntax is a section element with the following attributes and child elements:

<section>

</section>

Article Section

An Article Section relates a section independent to the surrounding sections.

The syntax is an article element with the following attributes and child elements:

<article>

</article>

Aside Section

An Aside Section relates an additional section that completes one or more surrounding sections.

It becomes a Complementary Landmark when in the direct context of a Content Window

The syntax is an aside element with the following attributes and child elements:

<aside>

</aside>

Navigation Section

A Navigation Section relates a section whose contents focus on a set of links to surrounding or descendant sections

It becomes a Navigation Landmark when in the direct context of a Content Window. In such context, the links should go to Content Windows outside of a web page

The syntax is a nav element with the following attributes and child elements:

<nav>

</nav>