Is it ensure, insure, or assure?
phagocytosis phag·o·cy·to·sis (fāg'ə-sī-tō'sĭs)
The engulfing and ingestion of bacteria or other foreign bodies by phagocytes.
process by which certain living cells called phagocytes ingest or engulf other cells or particles. The phagocyte may be a free-living one-celled organism, such as an amoeba, or one of the body cells, such as a leukocyte (white blood cell). In some forms of animal life, such as amoebas and sponges, phagocytosis is a means of feeding; in higher animals phagocytosis is chiefly a defensive reaction against infection and invasion of the body by foreign substances (antigens).