The font-size property determines the font size of an element.
The size can be set in several ways. The set of constants (xx-small, x-small, small, medium, large, x-large, xx-large) specifies the size, which is called absolute. In truth, they are not entirely absolute, as they depend on the settings of the browser and the operating system.
Another set of constants (larger, smaller) sets the relative font sizes. Since the size is inherited from the parent element, these relative sizes are applied to the parent element to determine the current element's font size.
Ultimately, the font size is highly dependent on the value of the font-size property on the element's parent.
font-size: absolute-size | relative-size | length | percentage;