What is the difference between sieving and winnowing?

Sieving and winnowing are both methods of separation, but they work on different principles and are used in different situations.

Sieving is based on the difference in particle size. It uses a sieve or mesh to separate smaller particles from larger ones. For example, separating fine flour from bran or sand from stones.

Winnowing is based on the difference in weight. It uses air to blow away lighter particles while heavier ones fall down. For example, separating husk from grains.

In simple terms, sieving is used when particles differ in size, while winnowing is used when they differ in weight.