The approximate extent of Old Norse and related languages in the early 10th century:
Old West Norse dialect
Old East Norse dialect
The Danish language develops during the Middle Ages out of the Old East Norse, the common predecessor of Danish and Swedish, itself a late form of common Old Norse. The history of Danish can by convention be divided into:
- Old Danish (Old East Norse), 9th to 11th centuries
- Middle Danish, 12th to 15th centuries
- Modern Danish, 16th century to present.
Old Danish 
Main article: Old East Norse
Old East Norse is in Sweden called Runic Swedish and in Denmark Runic Danish, but until the 12th century, the dialect was the same in the two countries. The dialects are called runic because the main body of text appears in the runic alphabet. Unlike Proto-Norse, which was written with the Elder Futhark alphabet, Old Norse was written with the Younger Futhark alphabet, which only had 16 letters. Due to the limited number of runes, some runes were used for a range of phonemes, such as the rune for the vowel u which was also used for the vowels o, ø and y, and the rune for i which was also used for e.
A change that separated Old East Norse (Runic Swedish/Danish) from Old West Norse was the change of the diphthong æi (Old West Norse ei) to the monophthong e, as in stæin to sten. This is reflected in runic inscriptions where the older read stain and the later stin. There was also a change of au as in dauðr into ø as in døðr. This change is shown in runic inscriptions as a change from tauþr into tuþr. Moreover, the øy (Old West Norse ey) diphthong changed into ø as well, as in the Old Norse word for "island".
Middle Danish 
From 1100 and onwards, the dialect of Denmark began to diverge from that of Sweden. The innovations spread unevenly from Denmark which created a series of minor dialectal boundaries, isoglosses, ranging from Zealand to Svealand.
Modern Danish 
The first translation of the Bible in Danish was published in 1550.
Some notable authors of works in Danish are existential philosopher Søren Kierkegaard, prolific fairy tale author Hans Christian Andersen, and playwright Ludvig Holberg. Three 20th century Danish authors have become Nobel Prize laureates in Literature: Karl Adolph Gjellerup and Henrik Pontoppidan (joint recipients in 1917) and Johannes Vilhelm Jensen (awarded 1944).
- "Language" (PDF). Royal Danish ministry of foreign affairs.