Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide  units bound together byglycosidic lankages and on hydrolysis give the constituent monosaccharide or oligosaccharides. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose and chitin.Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks. They may be amorphous or even insoluble in water.When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a homopolysaccharide or homoglycan, but when more than one type of monosaccharide is present they are called heteropolysaccharides or heteroglycans.
Its a carbohydrate that can be decomposed by hydrolysis into two or more molecules of monosaccharides, containing many monosaccharide units and marked by complexity