A _______ is the size of type as computed relative to the type size of the top level "html" element rather than a parent element.

The term that describes a unit of measurement for font size, specifically defined in relation to the font size of the top level "html" element, is "rem." The "rem" unit, which stands for "root em," allows developers to create a more consistent and scalable typographic system across a web page. By setting sizes in "rem," any adjustments to the font size of the root element (the "html" element) will consequently affect all text sizes defined in "rem," making it easier to maintain responsive designs.

In this context, using "rem" instead of other units, such as "em," is particularly beneficial because "em" references the font size of its immediate parent element instead of the top level. This characteristic of "rem" makes it a preferred choice for many developers looking to create a more predictable and manageable typography system in their web projects.