Matric suction is a very important concept in unsaturated soil mechanics
and it is not easy to understand its physics significance. The concept of matric suction and some questions on matric suction are discussed in this paper in term of basic formulae of surface physical chemistry
i.e. Young-Laplace formula and Kelvin formula. The rebuts indicate that the magnitude of matric suction in soils is controlled by aperture size
and it is interrelated with equilibrium retative humidity of the circumstances
and distribution curve of pore size determines the characteristics of the moisture retention curve.