Chapter 4: Definitions

A quick guide to common EPUB terms, HTML/XHTML elements, and CSS styling. Each bold term is paired with its meaning in regular text.

For example, h2 means heading level 2, and p means paragraph. Heading levels describe structure; CSS controls their appearance.

EPUB basics

EPUB: A digital publication format that packages content and supporting files into one .epub file.
EPUB 3: The EPUB standard’s third major generation.
Reading system: An app or device that opens and presents EPUB publications.
Reflowable layout: Text adapts to the available reading area and reader settings.
Fixed layout: Content uses a predetermined page arrangement.
Package document (.opf): The file describing publication metadata, resources, and reading order.
Metadata: Information describing a book, such as title, author, and language.
Manifest: The package’s list of publication resources.
Spine: The package’s ordered list of documents for reading.
Navigation document: The EPUB XHTML document containing the linked contents.
TOC: Table of contents: links to the book’s sections.
Landmarks: Navigation links to major book components.
container.xml: The file in META-INF that locates the package document.
mimetype: The file identifying the archive as application/epub+zip.
Media type: A resource’s format label, such as text/css.
Publication identifier: A value identifying the publication.
XHTML: HTML expressed using XML syntax.
CSS: Cascading Style Sheets: rules controlling presentation.
SVG: Scalable Vector Graphics: an XML-based image format.

html: The document’s root element, containing head and body.
head: Document information and resource links, outside the main reading content.
title: The document’s name, recorded inside head.
body: The document’s reading content.
link: Connects a document to a resource, commonly a stylesheet.
meta: Records document metadata.
style: Contains CSS rules within a document.
h1: Heading level 1: a top-level heading, commonly a chapter title.
h2: Heading level 2: a section heading below h1.
h3: Heading level 3: a subsection heading below h2.
h4: Heading level 4: a heading below h3.
h5: Heading level 5: a heading below h4.
h6: Heading level 6: the deepest numbered heading level.
section: A thematic section, usually with a heading.
nav: A section containing navigation links.
div: A generic block container with no specific meaning.

p: Paragraph. Example: Your paragraph here.
br: A line break within text; not a new paragraph.
hr: A thematic break, such as a change of scene.
strong: Text with strong importance; usually displayed in bold.
b: Text that draws attention without adding strong importance; usually bold.
em: Stressed emphasis; usually displayed in italics.
i: Text in an alternate voice or convention, such as a technical term; usually italic.
span: A generic inline container for a short piece of text.
blockquote: A quotation set apart from surrounding text.
q: A short inline quotation.
cite: The title of a referenced work.
code: A fragment of computer code or markup.
pre: Preformatted text that preserves spaces and line breaks.
sub: Subscript text, as in chemical formulas.
sup: Superscript text, as in exponents.
ul: An unordered list, usually shown with bullets.
ol: An ordered list, usually shown with numbers.
li: An item inside an ordered or unordered list.
dl: A description list pairing names or terms with descriptions.
dt: A term or name in a description list.
dd: The description associated with a term in a description list.

a: An anchor element; creates a hyperlink when it has an href attribute.
href: The destination address of a link.
id: An identifier unique within its document; can serve as a link target.
class: One or more labels used to group elements, often for styling.
src: The address of an image or other embedded resource.
alt: An image’s text alternative; decorative images normally use empty alt text.
img: Embeds an image.
figure: Self-contained content, such as an illustration with a caption.
figcaption: A caption for a figure.
table: Tabular data arranged in rows and columns.
caption: A table’s title or explanation.
thead: A group of table header rows.
tbody: A group of table body rows.
tr: A table row.
th: A table header cell.
td: A standard table data cell.
scope: Identifies the cells a table header applies to, such as its row or column.

Element: A structural component such as a paragraph, heading, or link.
Tag: Markup marking an element, such as or .
Attribute: A named value on an element, such as class="intro".
Opening tag: Begins an element; for example, .
Closing tag: Ends an element; for example, .
Empty element: An element with no content; XHTML examples include and <img/>.
Relative path: A file address resolved from the current location, such as CHAP-01.xhtml.
Fragment link: A link to an identified point, such as CHAP-01.xhtml#intro.
Selector: The part of a CSS rule that identifies what to style.
Property: A presentation setting in CSS, such as font-size.
Value: The setting assigned to a property, such as 1.2em.
font-family: The preferred typeface family or fallback families.
font-size: The size of text.
font-weight: The weight of text, such as normal or bold.
font-style: A font’s style, such as normal or italic.
line-height: The height used for each line of text.
margin: Space outside an element’s border.
padding: Space between content and its border.
text-align: The alignment of inline content, such as left or center.
Media query: A condition that applies styles for particular viewing circumstances.

These plain-language definitions summarize terminology; examples are provided for this template.