How can you tell if a fabric is 100% cotton?

There are three ways of telling if the fabric is 100% cotton.
1. The burn test: Cotton is a natural fibre. When burned, it leaves grey ash. It does not shrink when brought near the flame. Although, it would not be best to burn your newly obtained bed sheet.
2. Feel the fabric- Cotton is a soft fabric that is non-stretchable, breathable, and comfortable. There are several fabrics with a similar appearance. So, it would require more than a mere touch to judge.
3. Get it wet- Another property of cotton is its ability to hold water. Unlike synthetic fibres like polyester and nylon, it doesn\'t dry quickly. Cotton bed sheets are best for humid and hot days.