Just as with Bootstrap 3, Bootstrap 4 styles HTML's built-in abbr tag, which gives developers the ability to denote abbreviations. Denoting a piece of text as being an abbreviation will result in a small, dotted line being drawn underneath the text. As the user hovers over the text, the mouse pointer will change into a question mark. By setting the title attribute, a tool tip will appear with the full title attribute's text content:

<abbr title="My abbreviation">ABBR</abbr>