There are several different ways you can declare the size of a font in CSS. The units fall into one of two categories - absolute and relative.

Absolute units are fixed. Once they are declared, their size cannot be altered by changing the font size of some other element. Those include px, ­pt and pc units.

The size of relative units is determined by the size of a parent element. Their size can be altered by changing the sizing of that dependent element. Those include %, em, rem, vw, vh, vmin, vmax, etc.

What units do you normally prefer to use?