- See Classical languages of India for the term "classical languages" as used in Indian politics.
A classical language is a language with a literature that is classical. According to UC Berkeley linguist George L. Hart, it should be ancient, it should be an independent tradition that arose mostly on its own, not as an offshoot of another tradition, and it must have a large and extremely rich body of ancient literature.
Thus classical languages tend to be either dead languages, or show a high degree of diglossia, as the spoken varieties of the language diverge further and further away from the classical written language over centuries.
Classical studies 
In the context of traditional European classical studies, the "classical languages" refer to ancient Greek and Latin, which were the literary languages of the Mediterranean world in classical antiquity.
When we realize that an educated Japanese can hardly frame a single literary sentence without the use of Chinese resources, that to this day Siamese and Burmese and Cambodgian bear the unmistakable imprint of the Sanskrit and Pali that came in with Hindu Buddhism centuries ago, or that whether we argue for or against the teaching of Latin and Greek [in schools] our arguments are sure to be studded with words that have come to us from Rome and Athens, we get some indication of what early Chinese culture, Buddhism, and classical mediterranean civilization have meant in the world's history. There are just five languages that have had overwhelming significance as carriers of culture. These are classical Chinese, Sanskrit, Arabic, Greek, and Latin. In comparison with these, even such culturally important languages as Hebrew and French sink into a secondary position.
In this sense, a classical language is a language that has a broad influence over an extended period of time, even after it is no longer a colloquial mother tongue in its original form. If one language uses roots from another language to coin words (in the way that many European languages use Greek and Latin roots to devise new words such as "telephone", etc.), this is an indication that the second language is a classical language.
Living languages with a large sphere of influence are known as world languages.
General usage 
The following languages are generally taken to have a "classical" stage. Such a stage is limited in time and is considered "classical" if it comes to be regarded as a literary "golden age" retrospectively. Thus, Classical Greek is the language of 5th to 4th century BC Athens and, as such, only a small subset of the varieties of the Greek language as a whole. A "classical" period usually corresponds to a flowering of literature following an "archaic" period, such as Classical Latin succeeding Old Latin, Classical Sumerian succeeding Archaic Sumerian, Classical Sanskrit succeeding Vedic Sanskrit, Classical Persian[disambiguation needed] succeeding Old Persian. This is a partly a matter of terminology, and for example Old Chinese is taken to include rather than precede Classical Chinese. In some cases, such as those of Arabic and Tamil, the "classical" stage corresponds to the earliest attested literary variant.
- Classical Sumerian (literary language of Sumer, c. 26th to 23rd centuries BC)
- Middle Egyptian (literary language of Ancient Egypt from c. the 20th century BC to the 4th century AD)
- Old Babylonian (The Akkadian language from c. 20th to 16th centuries BC, the imitated standard for later literary works)
- Classical Hebrew (the language of the Tanakh, in particular of the prophetic books of c. the 7th and 6th centuries BC)
- Classical Chinese (based on the literary language of the Zhou Dynasty from c. the 5th century BC)
- Classical Greek (Attic dialect of the 5th century BC)
- Classical Sanskrit (described by Pāṇini's grammar, but used since c. 4th century BC) 
- Classical Tamil (Sangam literature c. 2nd century BC to 3th century AD, defined by Tolkāppiyam)
- Classical Pali (Buddhist Canon used this language from c. 3rd or 2nd centuries BC)
- Classical Latin (literary language of the 1st century BC)
- Classical Mandaic (literary Aramaic of Mandaeism, 1st century AD)
- Classical Syriac (literary Aramaic of the Syriac church, 3rd to 5th centuries)
- Middle Persian (court language of the Sassanid Empire, 3rd to 7th centuries)
- Classical Armenian (oldest attested form of Armenian from the 5th century and literary language until the 18th century)
- Middle Ages
- Old Javanese, (from the 9th century to present)
- Classical Tibetan (religious and literary language of Tibet, 8th century to present)
- Classical Arabic (based on the language of the Qur'an, 7th century)
- New Persian (language of classical Persian literature, 9th to 17th centuries)
- Classical Kannada (The earliest available literary work is the Kavirājamārga, 850 AD);
- Classical Japanese (language of Heian period literature, 10th to 12th centuries)
- Classical Malayalam (The earliest written record of Malayalam as distinct from Tamil is the Vazhappalli inscription, ca. 830 AD)
- Classical Telugu (The earliest available literary work is the Telugu Mahabharata, 1067 AD)
- Classical Icelandic (the language of the Icelandic sagas, 13th century)
- Classical Gaelic (language of the 13th to 18th centuries Scottish and Irish Gaelic literature)
- Pre-Colonial Americas
- Classical Maya (the language of the mature Maya civilization, 3rd to 9th centuries)
- Classical Quechua (lingua franca of the 16th century Inca Empire)
- Classical Nahuatl (lingua franca of 16th century central Mexico)
- Classical K'iche' (language of 16th century Guatemala)
- Classical Tupi (language of 16th to 18th centuries Brazil)
- Early Modern period
- Early Modern English (language of KJV Bible and Shakespeare, 16th to 17th centuries)
- Classical Ottoman Turkish (language of poetry and administration of the Ottoman empire, 16th to 19th centuries)
See also 
- Aureation, an aspect of the influence of a classical language on a later language
- Classical languages of India
- Literary language
- Sacred language
- Official language
- Standard language
- World language
- List of languages by first written accounts
- The Primary Classical Language of the World
- University of California-Berkeley
- Ramanujan, A. K. (1985), Poems of Love and War: From the Eight Anthologies and the Ten Long Poems of Classical Tamil, New York: Columbia University Press. Pp. 329, ISBN 0-231-05107-7Quote (p.ix–x) "Tamil, one of the four classical languages of India, is a Dravidian language ... These poems (Sangam literature, 1st century BC to 3rd century AD) are 'classical,' i.e. early, ancient; they are also 'classics,' i.e. works that have stood the test of time, the founding works of a whole tradition. Not to know them is not to know a unique and major poetic achievement of Indian civilization."
- Article "Panini" from The Columbia Encyclopedia (Sixth Edition. 2001-07) at Bartleby.com
- Zvelebil, Kamil (1997), The Smile of Murugan: On Tamil Literature of South India: On Tamil Literature of South India, BRILL Academic Publishers. p. 378, ISBN 90-04-03591-5 Quote: "Chart 1 literature: 1. the "Urtext" of the Tolkappiyam, i.e. the first two sections, Eluttatikaram and Collatikaram minus later interpolations, ca. 100 BC 2. the earliest strata of bardic poetry in the so-called Cankam anthologies, ca. 1 Cent. BC–2 Cent. AD."
- Encyclopædia Britannica, 2008. "Kannada literature" Quote: "The earliest literary work is the Kavirājamārga (c. AD 850), a treatise on poetics based on a Sanskrit model."
- Kannada gets classical tag