A small number of people in Cornwall have been brought up to be bilingual native speakers,[22][23] and the language is taught in schools and appears on street nameplates.

[32] The western dialects eventually evolved into modern Welsh and the now extinct Cumbric, while Southwestern Brittonic developed into Cornish and Breton, the latter as a result of emigration to parts of the continent, known as Brittany over the following centuries.

[35] The earliest written record of the Cornish language comes from this period: a 9th-century gloss in a Latin manuscript of De Consolatione Philosophiae by Boethius, which used the words ud rocashaas.

[51] Others are the Charter Fragment, the earliest known continuous text in the Cornish language, apparently part of a play about a medieval marriage,[52] and Pascon agan Arluth (The Passion of Our Lord), a poem probably intended for personal worship, were written during this period, probably in the second half of the 14th century.

This text is a late 16th century translation of twelve of Bishop Bonner's thirteen homilies by a certain John Tregear, tentatively identified as a vicar of St Allen from Crowan,[54] and has an additional catena, Sacrament an Alter, added later by his fellow priest, Thomas Stephyn.

The passing of this Act was one of the causes of the Prayer Book Rebellion (which may also have been influenced by government repression after the failed Cornish rebellion of 1497), with "the commoners of Devonshyre and Cornwall" producing a manifesto demanding a return to the old religious services and included an article that concluded, "and so we the Cornyshe men (whereof certen of us understande no Englysh) utterly refuse thys newe Englysh.

"[57] In response to their articles, the government spokesman (either Philip Nichols or Nicholas Udall) wondered why they did not just ask the king for a version of the liturgy in their own language.

[58] Archbishop Thomas Cranmer asked why the Cornishmen should be offended by holding the service in English, when they had before held it in Latin, which even fewer of them could understand.

[68] Archaeologia Britannica also features a complete version of a traditional folk tale, John of Chyanhor, a short story about a man from St Levan who goes far to the east seeking work, eventually returning home after three years to find that his wife has borne him a child during his absence.

[74] It is difficult to state with certainty when Cornish ceased to be spoken, due to the fact that its last speakers were of relatively low social class and that the definition of what constitutes "a living language" is not clear cut.

[76] However, although it is clear Davey possessed some traditional knowledge in addition to having read books on Cornish, accounts differ of his competence in the language.

"[78] The revival focused on reconstructing and standardising the language, including coining new words for modern concepts, and creating educational material in order to teach Cornish to others.

A process of unification was set about which resulted in the creation of the public-body Cornish Language Partnership in 2005 and agreement on a Standard Written Form in 2008.

[99] A study that appeared in 2018 established the number of people in Cornwall with at least minimal skills in Cornish, such as the use of some words and phrases, to be more than 3,000, including around 500 estimated to be fluent.

[109] Until around the middle of the 11th century, Old Cornish scribes used a traditional spelling system shared with Old Breton and Old Welsh, based on the pronunciation of British Latin.

[112] Old Cornish features include using initial ⟨ch⟩, ⟨c⟩, or ⟨k⟩ for /k/, and, in internal and final position, ⟨p⟩, ⟨t⟩, ⟨c⟩, ⟨b⟩, ⟨d⟩, and ⟨g⟩ are generally used for the phonemes /b/, /d/, /ɡ/, /β/, /ð/, and /ɣ/ respectively, meaning that the results of Brittonic lenition are not usually apparent from the orthography at this time.

The first sound change to distinguish Cornish from both Breton and Welsh, the assibilation of the dental stops /t/ and /d/ in medial and final position, had begun by the time of the Vocabularium Cornicum, c. 1100 or earlier.

[139] Several Celtic or Brittonic words cannot be reconstructed to Proto-Indo-European, and are suggested to have been borrowed from unknown substrate language(s) at an early stage, such as Proto-Celtic or Proto-Brittonic.

[140] Other words in Cornish inherited direct from Proto-Celtic include a number of toponyms, for example bre 'hill', din 'fort', and bro 'land',[141] and a variety of animal names such as logoden 'mouse', mols 'wether', mogh 'pigs', and tarow 'bull'.

[142] During the Roman occupation of Britain a large number (around 800) of Latin loan words entered the vocabulary of Common Brittonic, which subsequently developed in a similar way to the inherited lexicon.

)[136] The many English loanwords, some of which were sufficiently well assimilated to acquire native Cornish verbal or plural suffixes or be affected by the mutation system, include redya 'to read', onderstondya 'to understand', ford 'way', hos 'boot' and creft 'art'.

The grammatical features most unfamiliar to English speakers of the language are the initial consonant mutations, the verb–subject–object word order, inflected prepositions, fronting of emphasised syntactic elements and the use of two different forms for 'to be'.

There is an online radio and TV service in Cornish called Radyo an Gernewegva, publishing a one-hour podcast each week, based on a magazine format.

[178] In 2015 a university-level course aiming at encouraging and supporting practitioners working with young children to introduce the Cornish language into their settings was launched.

The Cornish Language Practice Project (Early Years) is a level 4 course approved by Plymouth University and run at Cornwall College.

[183] Since the onset of the COVID-19 pandemic a number of conversation groups entitled Yeth an Werin Warlinen have been held online, advertised through Facebook and other media.

[189] Early Modern Cornish was the subject of a study published by Lhuyd in 1707,[190] and differs from the medieval language in having a considerably simpler structure and grammar.

Conversely, along with government provision was the governmental basis of "New Public Management", measuring quantifiable results as means of determining effectiveness.

The Truro Waterstones hosts the annual Holyer an Gof literary awards, established by Gorsedh Kernow to recognise publications relating to Cornwall or in the Cornish language.

In 1987, however, they gave over 15 minutes of airtime on Sunday mornings for a programme called Kroeder Kroghen ('Holdall'), presented by John King, running until the early 1990s.