A greenhouse is a building made mostly of glass where plants are grown in controlled warmth and light. It protects plants from cold weather and lets gardeners grow plants out of season.
Formed in English from “green” + “house” in the 1600s to describe a house for growing green plants. Earlier versions were called “orangeries” when used for citrus trees.
The word “greenhouse” is literal: it’s simply a house that keeps plants green. The same idea is behind the term “greenhouse effect,” where Earth’s atmosphere acts like an invisible plant house trapping heat.
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