What is the term for the space between lines of text?

The term for the space between lines of text is leading. This typographic term refers to the vertical space between the baselines of consecutive lines of type. The term originated from the days of typesetting with physical lead strips that were placed between the lines of type to increase this spacing. Proper leading is crucial in enhancing readability and creating a visually appealing text layout, as it helps to create enough separation between lines so that they don’t blend into each other, allowing readers to follow the text more easily.

In contrast, kerning refers specifically to the adjustment of space between individual pairs of letters to improve visual consistency, while tracking involves adjusting the spacing uniformly across a range of characters. Spacing is a more general term that could refer to various forms of spacing in design but doesn't specifically address the space between lines of text. Thus, leading is the precise term that accurately describes this aspect of typography.