Type scale
A type scale is a set of font sizes generated by multiplying a base size by a consistent ratio at each step — for example 1rem, 1.333rem, 1.777rem using a perfect fourth (1.333).
Why it matters
When heading and body sizes are too close (below roughly 2:1), hierarchy requires reading. A modular scale creates preattentive structure — the eye knows what is a heading before parsing words.