The basic definition for this term is: group of two or more flowers on the same stalk or peduncle. An inflorescence can vary greatly in format, from the long spike, like the Gladioli, to the larger and rounder, like hydrangea. (Also see raceme, panicle, spike and umbel.)
Infructescence
Group of fruits developed by the development of the ovaries in the flowers from an inflorescence, like the pineapple or jack.
Internode
Space between nodes on a stem or branch
Iris
Received its name in homage of the Greek Goddess of the rainbow.
Aerial root: Roots derived from nodes. These roots are usually used by vines to climb, but also absorb humidity from the air. Many only develop properly if they manage to attach to a medium adequate to grow roots, like sphagnum. The philodendron and monstera are plants that present aerial roots.