The border-bottom property in CSS is used to set the properties of the bottom border of a box.
It is a shorthand property of the following:
border-bottom-widthborder-bottom-colorborder-bottom-styleborder-bottom: border-width border-style border-color|initial|inherit;
border-bottom-color: Sets or defines the color of the bottom border.
border-bottom-style: Specifies any style of the bottom border; the default value is none.
border-bottom-width: Specifies the width of the bottom border; the default value is medium.
initial: Sets the value to its default value.
inherit: Inherits property from its parent value.
The example below demonstrates the use of the border-bottom property. We use the border-bottom property to define the border to be nine pixels thick, dotted, and red.