What are macro-nutrients and why are they called macronutrients?

(N/A) Macronutrients are essential mineral elements that are required by plants in relatively large quantities for their growth and development.
They are called macronutrients because the term 'macro' implies 'large' or 'great', indicating that these nutrients are needed in significant amounts (usually in excess of $10 \text{ mmol kg}^{-1}$ of dry matter) compared to micronutrients.
Examples include:
$(i)$ $N, P, S$ which are essential components of proteins.
$(ii)$ $Ca$ which is a structural component of the cell wall.
$(iii)$ $Mg$ which is a central component of the chlorophyll molecule.