What Is Lowercase?
Lowercase letters are the small letters — a, b, c — used for most text. Their varied heights, with ascenders and descenders, create distinctive word shapes that make reading fast and comfortable. The name comes from the lower case where printers kept these more frequently used letters.
Because lowercase forms vary in height, fluent readers recognise whole words by silhouette rather than spelling out each letter — a major reason body text is set in lowercase.
The x-height of the lowercase largely determines how big and legible a font feels at a given point size.