Plants are a major group of living things including familiar organisms such as trees, flowers, herbs, ferns, and mosses. About 350,000 species of plants, defined as seed plants, bryophytes, ferns and fern allies, have been estimated to exist. As of 2004, some 287,655 species had been identified, of which 258,650 are flowering and 15,000 bryophytes. Plants are mostly autotrophs, organisms that obtain energy from sunlight or organisms that make their own food. Most plants carry out a process called photosynthesis, a process that occurs in the chloroplasts of plants.

Aristotle divided all living things between plants, which generally do not move, and animals. In Linnaeus' system, these became the Kingdoms Vegetabilia (later Plantae) and Animalia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these are still often considered plants in many contexts. Indeed, any attempt to match "plant" with a single taxon is doomed to fail, because plant is a vaguely defined concept unrelated to the presumed phylogenic concepts on which modern taxonomy is based.