What does "font size" refer to in document formatting?

Font size refers specifically to the height of characters in a typeface, which is measured in points. A point is a unit of measurement used in typography that equals about 1/72 of an inch. This measurement is crucial for document formatting because it impacts the readability and overall appearance of the text. Selecting an appropriate font size is essential for ensuring that the text is clear and accessible to readers, whether they are reading a printed document or viewing it on a screen.

The other choices refer to different aspects of text formatting: text style pertains to the design or appearance of the typeface (such as bold, italic, or underline), text color deals with the visible hue of the characters, and line spacing involves the amount of space between lines of text. Each of these elements contributes to the overall formatting and aesthetics of a document, but they do not define what font size is.