Why is price elasticity of demand always negative?

Price of demand(PED) is always negative because price of commodity and demand for that commodity has inverse relationship.

We know,

## PED = " %change in quantity"/" % change in price" ##

PED is negative because of law of demand i.e. increase in price of commodity decreases the quantity demand of that commodity or in other words positive change in price of a commodity has negative change in quantity demanded for that product.

This negative relation causes PED to become negative.