Lemon

The lemon is a species of small evergreen tree in the flowering plant family Rutaceae, native to Asia, primarily Northeast India (Assam), Northern Myanmar, and China. The tree's ellipsoidal yellow fruit is used for culinary and non-culinary purposes throughout the world, primarily for its juice, which has both culinary and cleaning uses. The pulp and rind are also used in cooking and baking. The juice of the lemon is about 5–6% citric acid, with a pH of around 2.2, giving it a sour taste. The distinctive sour taste of lemon juice, derived from the citric acid, makes it a key ingredient in drinks and foods such as lemonade and lemon meringue pie.

Source: Wikipedia