abbr: The Abbreviation element
When including an abbreviation or acronym, provide a full expansion of the term in plain text on first use, along with the <abbr> to mark up the abbreviation. This informs the user what the abbreviation or acronym means.
The optional title attribute can provide an expansion for the abbreviation or acronym when a full expansion is not present. This provides a hint to user agents on how to announce/display the content while informing all users what the abbreviation means. If present, title must contain this full description and nothing else.
Attributes
Specific attributes
title="[meaning of abbreviation]" The title attribute has a specific semantic meaning when used with the <abbr> element; it must contain a full human-readable description or expansion of the abbreviation. This text is often presented by browsers as a tooltip when the mouse cursor is hovered over the element.
Global attributes
role="[semantic-role]"
accesskey="[key]"
class="[classname]"
dir="[auto/ltr/rtl]"
id="[identifier]"
itemid="[global-identifier]"
itemprop="[property-name]"
itemscope itemtype="[url of the vocabulary]"
lang="[language-code]"
tabindex="[num index]"
title="[Title]"
Example
<p>I like <abbr title="HyperText Markup Language">HTML</abbr>!</p>