Citrus limetta

Citrus limetta, alternatively considered to be a cultivar of Citrus limon, C. limon 'Limetta'. is a species of citrus, commonly known as mousami, musami, sweet lime, sweet lemon, and sweet limetta, it is a member of the sweet lemons. It is small and round like a common lime in shape. It is a cross between the citron (Citrus medica) and a bitter orange (Citrus × aurantium). 
It is native to southern regions of Iran and also cultivated in the Mediterranean Basin.
In Iran it is called limu shirin (لیمو شیرین, meaning 'sweet lemon' in Persian).
In India, it is commonly called mausambi, mosambi, or musambi in Hindi ( Moushumi or mushumbilebu) in Bengali  satukudi or satukodi in Tamil, (in Hindi and Marathi), musambi in Kannada, battayi in Telugu, chinikaya in Rayalaseema, and musambi in Malayalam.
In Bangladesh, it is called musambi or mosambi, in Bengali).
In Nepali, it is called mausam.
In Pakistan, usually, it is called musami (موسمى, in Urdu).
In the Sindh, it is known as mosami.
Among Iraqi Armenians, it is called noumi.
In France, it is sometimes called bergamot; it should not be confused with Citrus bergamia, the bergamot orange. 
It is a different fruit from the Palestinian sweet lime and from familiar sour limes such as the Key lime and the Persian lime. However, genomic analysis revealed it to be highly similar to the Rhobs el Arsa, and the two likely represent progeny of distinct crosses of the same citrus parents. 

Flavour
Freshly pressed sweet lime juice as served in the Indian subcontinent. As the name sweet lime suggests, the flavour is sweet and mild, but retains the essence of lime. The lime's taste changes rapidly in contact with air, and will turn bitter in few minutes,[citation needed] but if drunk soon after being juiced, the taste is sweet. The flavour is a bit flatter than most citrus due to its lack of acidity. It can be compared to limeade and pomelo.

Uses
    Sweet lime is served as juice and is good as a mixer for vodka. It is the most common available citrus juice in the Indian subcontinent. The juice is commonly sold at mobile road stalls.
    Like most citrus, the fruit is rich in vitamin C, providing 50 mg per 100 g serving.[8] In Iran it is popular as a house remedy to treat influenza and the common cold.
    The tree is used for ornamental purposes as well as for graft stock.

Checking for ripeness
Like most citrus, sweet limes will not ripen off the tree, and must be picked when fully ripe. This is indicated by its tennis ball size and lustrous greenish yellow sheen. Gently scratch the surface of a sweet lime: If its oils give way in the fingernails, it is ripe. The juiciest fruits feel heavy for their size. Underripe fruit feels light for its size, and is hard with tart flesh. Overripe fruit is dull and shrunken, with dry, spongy skin. Avoid fruit with brownish-yellow discoloration.

Storage
Sweet limes keep fresh for up to two weeks at room temperature, and four to eight weeks refrigerated. Frozen juice will keep for up to six months. It is possible to freeze slices of the fruit, though the limonin content may cause the pulp to taste bitter over time. This can be avoided by submerging the slices in sweet syrup within an airtight glass jar.
Sweet lemons are an excellent source of vitamin C to strengthen the immune system while reducing inflammation and contain other nutrients, including vitamin A, fiber, calcium, potassium, folate, and niacin. Sweet lemon and sweet lime refer to groups of citrus hybrids that contain low acid pulp and juice. They are hybrids often similar to non-sweet lemons or limes, but with less citron parentage. Sweet limes and lemons are not sharply separated:
 The sweet lime, Citrus limettioides Tan. (syn. C. lumia Risso et Poit.), is often confused with the sweet lemon, C. limetta Tan. (q.v. under LEMON) which, in certain areas, is referred to as "sweet lime". In some of the literature, it is impossible to tell which fruit is under discussion. The same plant may also be known by different names. The Indian sweet lime is the mitha nimbu (numerous modifications and other local names) of India, the limûn helou or succari of Egypt, and the Palestine sweet lime (to distinguish it from the Millsweet and Tunisian limettas, commonly called sweet limes). The sweet lemons and sweet limes are not derived from either lemons or the more common limes, nor do they represent a monophyletic grouping, having arisen from distinct citrus hybridizations. Plants and fruits with the common name sweet lemon or sweet lime include: Citrus limetta, small and round like a common lime, with sweet juice, a citron/sour orange hybrid. Lumia, a large dry citron-like fruit that is pear shaped and not necessarily sweet. This is itself a mixed group: one member has been found to have resulted from a lemon crossing with a citron/pomelo hybrid, a second member is a micrantha/citron mix. Palestinian sweet lime, Citrus × latifolia, mainly used as a rootstock, a citron/mandarin/pomelo hybrid.
Ujukitsu, Citrus ujukitsu, or 'lemonade fruit', likely a tangelo, a Kishu mikan crossed with a pomelo-like fruit, produced by citrus pioneer Chōzaburō Tanaka.