Lime has two main meanings:

1. A small, green citrus fruit with a sour, tangy flavor. Limes look like small green lemons and grow on trees in warm climates. Their juice adds bright flavor to foods and drinks: you might squeeze lime over tacos, stir it into lemonade, or use it in key lime pie. Sailors on long voyages once ate limes to prevent a disease called scurvy, which is why British sailors were nicknamed “limeys.” The fruit's sharp taste comes from citric acid, the same substance that makes lemons sour.
2. A white powder made from limestone, used in building and agriculture. When builders make cement or plaster, lime is often one of the ingredients. Farmers spread lime on soil to help crops grow better. This kind of lime is also called quicklime or calcium oxide, and it's created by heating limestone in special ovens. Unlike the fruit, this lime isn't edible and can burn your skin if you touch it.