"Yona" (also sometimes "Yonaka") is a Pali word used in ancient India to designate ancient Greek people. Its equivalent in Sanskrit is the word "Yavana". "Yona" and "Yavana" are both transliterations of the Greek word for "Ionians" (Homer Iāones, older *Iāwones), who were probably the first Greeks to be known in the East.
Even long before Alexander's invasion, the Greek settlements had existed in eastern parts of Achaemenid empire, north-west of India, as neighbors to the Iranian Kambojas. The references to the Yonas in the early Buddhist texts may be related with the same.
There are important references to the warring Mleccha hordes of the Shakas, Yavanas, Kambojas, Pahlavas etc in the Bala Kanda of the Valmiki Ramayana also (1.54.21-23; 1.55.2-3).
Foremost Indologists like Dr H. C. Raychadhury clearly see in these verses the glimpses of the struggles of the Hindus with the mixed invading hordes of the barbaric Sakas, Yavanas, Pahlavas, Kambojas etc from north-west. The time frame for these struggles is second century BCE downwards. Dr Raychadhury fixes the date of the present version of the Valmiki Ramayana around/after second century CE (Political History of Ancient India, 1996, p 3-4).
The other Indian records describe the 180 BCE Yavana attacks on Saketa, Panchala, Mathura and Pataliputra, probably against the Sunga empire, and possibly in defense of Buddhism. The main mentions of the invasion are those by Patanjali around 150 BCE, and of the Yuga Purana, which, like the Mahabharata, also describes Indian historical events in the form of a prophecy:
The Anushasanaparava of Mahabharata affirms that the country of Mathura, the heartland of India, was under the joint military control of the Yavanas and the Kambojas (12/101/5).
From the references noted above, it appears certain that the Yavana invasion of Majjhimadesa (Mid India) was jointly carried out by the Yavanas and the Kambojas. The Greek Yavavas were apparently a minority foreigners in India and naturally may have obtained, in this invasion, the military support of their good neighbors, the warlike Kambojas. The evidence from the Mathura Lion Capital inscriptions of Saka great Satrap (Mahakshatrapa) Rajuvula also lends strong credibility to this view.
The Mid India invasion was followed by almost two centuries of Yavana rule which in the light of evidence presented above, appears to have been a joint Yavana-Kamboja rule.
The Mahabharata compliments them as "the all-knowing Yavanas" (sarvajnaa yavanaa).
i.e. "The Yavanas, O king, are all-knowing; the Suras are particularly so. The mlecchas are wedded to the creations of their own fancy."
The "Brihat-Samhita" of the mathematician Varahamihira says: "The Greeks, though impure, must be honored since they were trained in sciences and therein, excelled others....." . e.g:
Yet another Indian text, (Gargi-Samhita), also similarly compliments the Yavanas saying: "The Yavanas are barbarians yet the science of astronomy originated with them and for this they must be reverenced like Gods" (Gargi-Samhita).
The Mahavamsa also attests Yona settlement in Anuradhapura in ancient Sri Lanka, probably contributing to trade between East and West.
Buddhist texts like Sumangala Vilasini class the language of the Yavanas with the Milakkhabhasa i.e impure language.
The Mahabharata groups the Yavanas with the Kambojas and the Chinas and calls them "Mlechchas" (Barbarians). In the Shanti Parava section, the Yavanas are grouped with the Kambojas, Kiratas, Sakas, and the Pahlavas etc and are spoken of as living the life of Dasyus (slaves). In another chapter of the same Parava, the Yaunas, Kambojas, Gandharas etc are spoken of as equal to the "Svapakas" and the "Grddhras".
Udyogaparava of Mahabharata (5/19/21-23) says that the composite army of the Kambojas, Yavanas and Sakas had participated in the Mahabharata war under the supreme command of Kamboja king Sudakshina. The epic numerously applauds this composite army as being very fierce and wrathful.
Balakanda of Ramayana also groups the Yavanas with the Kambojas, Sakas, Pahlavas etc and refers to them as the military allies of sage Vishistha against Vedic king Vishwamitra (55/2-3). The Kishkindha Kanda of Ramayana locates the Sakas, Kambojas, Yavanas and Paradas in the extreme north-west beyond the Himavat (i.e. Hindukush) (43/12).
The Buddhist drama Mudrarakshas by Visakhadutta as well as the Jaina works Parisishtaparvan refer to Chandragupta's alliance with Himalayan king Parvatka. This Himalayan alliance gave Chandragupta a powerful composite army made up of the frontier martial tribes of the Shakas, Kambojas, Yavanas, Parasikas, Bahlikas etc (See: Mudrarakshas, II) which he utilised to defeat the Greek successors of Alexander the Great and the Nanda rulers of Magadha, and thus establishing his Mauryan Empire in northern India.
Manusmriti (X/43-44) lists the Yavanas with the Kambojas, Sakas, Pahlavas, Paradas etc and regards them as degraded Kshatriyas (members of the warrior cast). Anushasanaparava of Mahabharata (13/33/23) also views the Yavanas, Kambojas, Shakas etc in the same light. Patanjali's Mahabhasya (II.4.10) regards the Yavanas and Sakas as anirvasita (pure) Shudras. Gautama-Dharmasutra (IV.21) regards the Yavanas or Greeks as having sprung from Shudra females and Kshatriya males.
The Assalayana Sutta of Majjhima Nikaya attests that in Yona and Kamboja nations, there were only two classes of people...Aryas and Dasas...the masters and slaves, and that the Arya could become Dasa and vice versa. The Vishnu Purana also indicates that the "chatur-varna" or four class social system was absent in the lands of Kiratas in the East and the Yavanas and Kambojas etc in the West.
Numerous Puranic literature groups the Yavanas with the Sakas, Kambojas, Pahlavas and Paradas and refers to the peculiar hair styles of these people which were different from those of the Hindus. Ganapatha on Panini attests that it was a practice among the Yavanas and the Kambojas to wear short-cropped hair (Kamboja-mundah Yavana-mundah).
Vartika of Katayana informs us that the kings of the Shakas and the Yavanas, like those of the Kambojas, may also be addressed by their respective tribal names.
Brihat-Katha-Manjari of Kshmendra (10/1/285-86) informs us that king Vikramaditya had unburdened the sacred earth of the Barbarians like the Shakas, Kambojas, Yavanas, Tusharas, Parasikas, Hunas etc by annihilating these sinners completely.
The Brahmanda Purana (Upodghata-pada, 16-17) refers to the horses born in Yavana country.
The Mahaniddesa (pp 155, 415) speaks of Yona and Parama Yona, probably referring to Arachosia as the Yona and Bactria as the Parama Yona.