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plant:

A many-celled living thing that usually makes its own food from carbon dioxide and water using light energy during a process called photosynthesis. Plants have thick cell walls that contain cellulose and are the primary source of food for all other living things. Plants include familiar living things such as trees, bushes, grasses, vines, ferns, mosses and green algae. The scientific study of plants is called botany. Nearly 300,000 different species of plants have been identified. At one time all living things were considered to belong to either the plant or the animal kingdom. The major difference between the two kingdoms was thought to be that plants can manufacture their own food while animals cannot, and plants cannot move about while animals can. But even this simple distinction is not always true; some kinds of one-celled living things seem to have the characteristics of both plants and animals. For example, a euglena, a one-celled organism, moves about in water but also contains chlorophyll and manufactures its own food. Today, most scientists consider plants to be only those more complex many-celled living things that can perform photosynthesis. Widely in use today is a five-kingdom system of classification: animals, plants, fungi, protists, and monerans. A euglena is now considered a protist.