# What is the difference between an Ordinary Demand equation and an Engel curve equation?

I mean, an Ordinary Demand Equation measures changes in quantity of X due to changes in price Px. Engel Curve measures changes in quantity of X due to changes in income M. But ODE has M in it's equation, and is simply just an algebraic variant of the Engel curve!

• Engel curve assumes the price is constant, and demand curve assumes income constant. There is only demand function, no engel curve equation or demand equation. – Kun Feb 14 '16 at 2:43
• You are very welcome – Kun Feb 14 '16 at 21:54