Accessibility Glossary

Print Disability

A condition (such as blindness, visual-impairment, learning disability, or mobility impairment), that limits a person's ability to read 'standard' printed material.

"Standard" means print that is not in a specialized format.


The characteristic of printed material that enables a person with a print disability to read it as effectively as a person without a disability.

Different print disabilities have different, sometimes overlapping, accessibility needs: large-print can be accessible to a person with a visual-impairment, audio can be accessible to a person who is blind, braille can be accessible to a person who is blind and deaf, and electronic text can be accessible to a person with a learning disability. Accessibility results when the individual's needs are met by the form, content, and structure of the material.

Specialized format

A format, such as large-print and braille, used primarily by people with print disabilities.

Formats such as audio and electronic text may be accessible, but are not in themselves specialized.

Assistive technology (AT)

Hardware and software used to create accessibility by modifying or converting printed material to another format.

A scanner, combined with software, can convert a printed book into electronic text, while another program could convert that text to speech (see below) or braille.

Text-to-speech (TTS)

The process of a computer reading text aloud ('synthetic speech')

TTS has improved to sound more human, but is still recognizably synthetic. Some commercial ebooks use DRM to control whether or not TTS can be used for that ebook (enabled versus not enabled).


A digital format designed to be accessible.

The DAISY Standard was developed for accessible publications, and the accessibility features of DAISY are incorporated into EPUB 3, which is a mainstream publishing standard.


A standard for digital publishing.

EPUB can support accessibility but currently many EPUBs are distributed with DRM that impedes their compatibility with assistive technology.


A standard for data about books.

ONIX was created primarily to help publishers, distributors, and retailers exchange information about books, such as title, author, format, price, etc. ONIX now has fields to track accessibility information if the publisher supplies it.

Digital Rights Management (DRM)

Software used to control how a digital file, such as an ebook, can be used

A buyer usually has to install DRM software that manages access to the file. Commonly, DRM controls how many copies of a file may be made to prevent unauthorized distribution. While not designed to block accessibility, DRM may prevent assistive technology from converting an ebooks text into speech, or otherwise making the ebook more accessible.

Alternate Text (Alt-text)

A written description of a picture, illustration, or other visual element.

Alt-text may also be used to describe something that would not be otherwise accessible using a screen reader or other AT (for example, a math equation that is displayed as an image). Alt-text is usually provided for its educational value, as in a textbook, so it should not repeat information that is available in the text or a caption. Alt-text may be stored with a file or web page so that it is readable using AT but not otherwise visible.


The ability to move from one part of a book to another based on a table of contents, index, page numbers, bookmarks, chapter or section headings, or other markers.

This is critical for textbooks which are often used more like reference works. Examples of accessible navigation could be buttons to skip to the next section heading, or a 'go to page' function. Navigation is generally enabled by tags (see below).

Logical reading order

An established, consistent sequence that material on a page will be read by assistive technology.

For example, if the text on a page is broken up with images and also has a sidebar with additional text, tags can be used to establish a logical sequence for the material to be presented to the reader Without such tags, the default reading sequence may confuse the reader with unexplained jumps.


Markers that control how an ebook or other digital document is displayed, navigated, and otherwise understood by a reader's software

Generally, tags are not made visible to the reader, but are used by software 'behind the scenes', to control the reading experience. There are various types of tags and tagging systems, such as HTML and XML. A tag in XML could be as simple as , indicating the beginning of a chapter in a book. Tags are critical to accessibility and should be as carefully considered and managed as the book's content.