noun, plural: flowers
Flowers are plant structures involved in sexual reproduction. Thus, they are typically comprised of sexual reproductive structures (i.e. androecium and gynoecium) in addition to nonessential parts such as sepals and petals. And the presence/absence of these structures may be used to describe flowers and flowering plants (angiosperms).
Complete and incomplete flowers:
Flowers that have these four structures are called complete; those lacking in one or more of these structures are called incomplete. Many flowering plants produce conspicuous, colorfoul, scented petals in order to attract insect pollinators. There are plants, like grasses, that produce flowers that are less-conspicuous and lacking in petals. These plants do not require insects but rely on other agents of pollination, such as wind.
Perfect (bisexual) and imperfect (unisexual) flowers:
Flowers that have both male and female reproductive structures are called bisexual or perfect. Flowers that bear either male (androecium) or female reproductive structures (gynoecium) are referred to as unisexual or imperfect. With only one reproductive organ present, imperfect flowers are also described as incomplete flowers.
Regular and irregular flowers:
Flowers that display symmetry are described as regular flowers in contrast to irregular flowers that do not.
Monoecious and dioecious plants:
Plants may be described as monoecious or dioecious. A monoecious plant bears both male and female imperfect flowers. A dioecious plant is a plant producing only one type of imperfect flowers, i.e. male or female flowers. Therefore, a dioecious plant may either be a male or female plant depending on the flower they produce.