Is it ensure, insure, or assure?
Fungi Fun·gi (fŭn'jī, fŭng'gī)
A kingdom of plantlike sporeforming organisms that grow in irregular masses without roots, stems, leaves, or photosynthetic.
Plantlike organisms lacking chlorophyll, such as mushrooms, molds, yeasts, and mildews. Modern biologists tend to place fungi in their own kingdom, not in the plant kingdom, because they get their nutrients from other living things (or from the remains of living things that have died) rather than from photosynthesis. (See under “Medicine and Health.”)