Spacing

Tailwind's numeric step scale, used as-is. A number is a name that resolves to one fixed value, which makes it a closed set exactly like a t-shirt scale would be.

import from Tailwind --spacing

Numeric is still a closed set

The principle requires that a value come from a finite named set, not that the names be words. mt-4 qualifies: 4 names one fixed value, and the only way out of the scale is the bracket — mt-[13px] — which the lint gate blocks. The wall against arbitrary values is the lint rule, not the naming style.

Name by intent only where a role actually recurs. A numeric step is right for one-off layout that has no reusable intent to name.

The scale

w-4
w-8
w-12
w-16
w-24
w-32
w-48
w-64

Reference

Step Value
1 0.25rem
2 0.5rem
3 0.75rem
4 1rem
6 1.5rem
8 2rem
12 3rem
16 4rem
24 6rem
32 8rem

Reading measure

One named width caps line length: max-w-measure (40.625rem). This paragraph is set to it. Long-form copy uses it, or the measure prop on Body, which is the same value. There is no second reading width and no arbitrary max-w-[40rem].

Target size

Interactive targets have a minimum size, and that is a constraint on the spacing scale rather than a separate checklist. A control smaller than the minimum is not a member of the set.