Look up greenhouse in Wiktionary, the free dictionary.

In horticulture, a greenhouse is a structure designed to regulate the temperature and humidity of the environment inside it with a view to growing plants. There are different types of greenhouses, but they all have large areas covered with transparent materials that let sunlight enter and that inhibit the loss of the sun's heat. The most common materials used in modern greenhouses for walls and roofs are rigid plastics made of polycarbonate, plastic film made of polyethylene, or glass panes. When sunlight shines into a greenhouse the temperature inside increases, providing a sheltered environment for plants to grow — even in cold weather.

The terms greenhouse, glasshouse, and hothouse often refer interchangeably to buildings used for cultivating plants. The specific term used depends on the material and on the heating-system used in the building. Nowadays, greenhouses are more commonly constructed with a variety of materials, such as wood and polyethylene plastic. A glasshouse, on the other hand, is a traditional type of greenhouse which uses glass panes that allow light to enter. The term hothouse indicates the use of artificial heating. However, both heated and unheated structures can generally class as greenhouses.

The word "vinery", when referring to a site for growing grapevines, may reference either a hothouse or a glasshouse.

Greenhouses can range in size from small sheds to industrial-sized buildings and colossal glasshouses. The smallest example is a miniature greenhouse known as a cold frame, typically used at home (compare cloche). Large commercial greenhouses are high-tech production-facilities used to grow vegetables, flowers or fruits. Such glass greenhouses may feature extensive equipment, including screening, heating, cooling, and lighting installations, sometimes controlled by a computer to optimize conditions for plant growth. Different techniques manage growing conditions (including air temperature, relative humidity and vapour-pressure deficit) in order to provide the optimum environment for cultivation of a specific crop.