Grass is the common word that generally describes monocotyledonous green plants. The family Gramineae (Poaceae) are the "true Grasses"
and include most plants grown as grains, for pasture, and for lawns
(turf). They include some more specialised crops such as lemonGrass, as well as many ornamental plants. They also include plants often not recognized to be Grasses, such as bamboos or some species of weeds called crab Grass.
The term Grass is often used to describe related plants in the rush (Juncaceae) and sedge (Cyperaceae) families, that somewhat resemble Grass. It may also be used to describe completely unrelated plants, sometimes of similar appearances to Grass,
with leaves rising vertically from the ground, and sometimes of
dissimilar appearance. The term came about in the early 15th century,
from the Old English græs, derived from the same root as "grow". A
single piece of Grass is called a blade.