The border-bottom-width property in CSS is used to set a specific width to the bottom border of an element. The border-bottom-style or border-style property is used for the element before using the border-bottom-width property.
Always declare the border-style or the border-bottom-style property before the border-bottom-width property. An element must have borders before you can change the width.
Syntax:border-bottom-width: length|thin|medium|thick|initial|inherit;
Property Values: The border-bottom-width property values are listed below: