The carefully-designed quantity of space between lines of words that allows us to read paragraphs easily.
This is called leading in the land of visual communication/typographers and graphic designers. It is technically the distance between two baselines (the imaginary line that all the letters sit on for a line of text) of type. The term leading in this manner originates from the strips of lead hand-typesetters used to space out lines of text evenly.
Proper leading can be the difference between someone wanting to read information and no one being able to read it at all. A basic rule of thumb when working with leading is that the line space amount is 2 points over the type size. If the type or letter size is 12 point, then your leading would be 14 point.
Line space examples:
- Standard: 12-point type, 14.5-point leading
- Better: 12-point type, 16-point leading
- Bad: 12-point type, 12-point leading
- More: 12-point type, 18-point leading
Information courtesy Jennifer Foy, Unisub