What is the main difference between a dwarf shrub and a shrub?

What is the main difference between a dwarf shrub and a shrub? How are shrubs like perennial grasses? How do dwarf shrubs differ from shrubs?

Shrubs differ from shrubs, first of all, in size. The shrub grows up to 6 m (lilac, hawthorn), and the shrub up to 80 cm (blueberry, blueberry). Semi-shrubs (currants, raspberries) are similar to perennial grasses (clover, mustard) in that the upper parts of these plants die off for the winter, but the roots are preserved. New shoots appear in the spring. In shrubs, the lower part of the plant is preserved for the winter. In shrubs, all branches are preserved for the winter.