Grass is a common word that generally describes a monocotyledonous green plant in the family Gramineae (Poaceae). True grasses 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, and some weeds. They also include plants often not considered to be grasses, such as bamboos.
The term 'grass' is sometimes used to describe related plants in the rush (Juncaceae) and sedge (Cyperaceae) families, that resemble grass somewhat. It may also be used to describe other unrelated plants, sometimes of similar appearances to grass, with leaves rising vertically from the ground, and sometimes of dissimilar appearance.
Grasses and grass-like plants have proven to be among the most versatile of life forms, thriving on every continent including Antarctica. Plants having grasslike structures have existed for millions of years, providing fodder for Cretaceous dinosaurs, whose fossilized dung (coprolite) contains phytoliths of a variety of grasses that include the ancestors of rice and bamboo (Piperno & Sues, 2005). Grasses have adapted to conditions in lush rain forests, dry deserts, and cold mountain steppes, and are presently the most widespread of all plant types. Plants of this type have always been important to human beings. They provide the majority of food crops, and have numerous other uses, such as feeding animals, and for lawns. There are numerous minor uses, and grasses are familiar to most human cultures.