When MRS is constant x and y are :
Not related
Perfect Substitutes
Perfect Complements
Inferior Goods
Smoothness of indifference curve means
X and Y are substitutes of each other
X and Y can be consumed in fixed proportion
Perfect divisibility of two goods
Perfect non divisibility of two goods
Decreasing slope of indifference curve is explained by
Law of diminishing marginal returns
Law of diminishing MRS
Law of demand
Law of constant MRS