A monosaccharide, C₆H₁₂O₆, stereoisomeric with glucose, that occurs naturally only in polymerized forms called mannans. These consist exclusively of mannose residues (linear mannans) or a combination of mannose and glucose residues (glucomannans), sometimes with galactose side chains. They are found in plants, algae, and fungi, serving as energy stores in seeds and roots. They are also major components of hemicelluloses, which play important structural roles in plants, especially gymnosperms. Mannans on the cell walls of Candida yeasts are involved in establishing infections and in triggering the body’s immune response.