The lemon is a small tree (Citrus limon) that is green even in the winter. It came from Asia. 'Lemon' is also the name of the tree's oval-shaped yellow fruit. The fruit is used for cooking and other things in the world – usually for its juice. Lemons contain numerous phytochemicals, including polyphenols, terpenes, and tannins. 

The lemon (Citrus × limon) is a species of small evergreen tree in the Citrus genus of the flowering plant family Rutaceae. A true lemon is a hybrid of the citron and the bitter orange. Its origins are uncertain, but some evidence suggests lemons originated during the 1st millennium BC in what is now northeastern India. Some other citrus fruits are called lemon.