Momordica charantia, known as bitter melon, bitter gourd, bitter squash, or balsam-pear, is a tropical and subtropical vine of the family Cucurbitaceae, widely grown in Asia, Africa, and the Caribbean for its edible fruit. Its many varieties differ substantially in the shape and bitterness of the fruit. Bitter melon also has names in other languages which have entered English as loanwords, e.g. kǔguā (苦瓜) from Chinese, nigauri (苦瓜) from Japanese, gōyā  from Okinawan, kaipakka in Malayalam, kakarakaya (కాకరకాయ) in Telugu, Hāgala (ಹಾಗಲ) in Kannada, pākal (பாகல்) in Tamil and karela (करेला and كاريلا) or kareli in Hindustani (Hindi and Urdu), coming from Sanskrit. In Bengali, it is known as uchche (উচ্ছে). Those from the Caribbean island of Jamaica commonly refer to the plant as cerasee. In Brazil this plant is called Saint Cajetan’s Melon .
Bitter melon originated in India and was introduced into China in the 14th century. It is widely used in East Asian, South Asian, and Southeast Asian cuisine.
This herbaceous, tendril-bearing vine grows up to 5 m (16 ft) in length. It bears simple, alternate leaves 4–12 cm (1.6–4.7 in) across, with three to seven deeply separated lobes. Each plant bears separate yellow male and female flowers. In the Northern Hemisphere, flowering occurs during June to July and fruiting during September to November.
The fruit has a distinct warty exterior and an oblong shape. It is hollow in cross-section, with a relatively thin layer of flesh surrounding a central seed cavity filled with large, flat seeds and pith. The fruit is most often eaten green, or as it is beginning to turn yellow. At this stage, the fruit’s flesh is crunchy and watery in texture, similar to cucumber, chayote or green bell pepper, but bitter. The skin is tender and edible. Seeds and pith appear white in unripe fruits; they are not intensely bitter and can be removed before cooking.
Some sources claim the flesh (rind) becomes somewhat tougher and more bitter with age, but other sources claim that at least for the common Chinese variety the skin does not change and bitterness decreases with age. The Chinese variety are best harvested light green possibly with a slight yellow tinge or just before. The pith becomes sweet and intensely red; it can be eaten uncooked in this state, and is a popular ingredient in some Southeast Asian salads.
When the fruit is fully ripe, it turns orange and mushy, and splits into segments which curl back dramatically to expose seeds covered in bright red pulp.