apoptosis: a type of cell death in which the cell uses specialized cellular machinery to kill itself; a cell suicide mechanism that enables metazoans to control cell number and eliminate cells that threaten the animal's survival
physical entity: an entity that has physical existence
flag smut fungus: a smut fungus causing a smut in cereals and other grasses that chiefly affects leaves and stems and is characterized chains of sori within the plant tissue that later rupture releasing black masses of spores