[3] From the seventh and eighth to the fifteenth and sixteenth centuries, the Mongolian language separated into southern, eastern and western dialects.

The principal documents from the period of the Middle Mongol language are: in the eastern dialect, the famous text The Secret History of the Mongols, monuments in the Square script, materials of the Chinese–Mongolian glossary of the fourteenth century and materials of the Mongolian language of the middle period in Chinese transcription, etc.

[2]: 545 Traditional Mongolian words are written vertically from top to bottom, flowing in lines from left to right.

This developed because the Uyghurs rotated their Sogdian-derived script, originally written right to left, 90 degrees counterclockwise to emulate Chinese writing, but without changing the relative orientation of the letters.

[5][1]: 36 The reed pen was the writing instrument of choice until the 18th century, when the brush took its place under Chinese influence.

Ink used was black or cinnabar red, and written with on birch bark, paper, cloths made of silk or cotton, and wooden or silver plates.

It does not distinguish several vowels (o/u, ö/ü, final a/e) and consonants (syllable-initial t/d and k/g, sometimes ǰ/y) that were not required for Uyghur, which was the source of the Mongol (or Uyghur-Mongol) script.

[5] The result is somewhat comparable to the situation of English, which must represent ten or more vowels with only five letters and uses the digraph th for two distinct sounds.

[4]: 30, 73 [24]: 12 [30][31][25]: 28 [28]: 534 Such single-letter vowel suffixes appear with the final-shaped forms of a/e, i, or u/ü,[4]: 30  as in ᠭᠠᠵᠠᠷ ᠠ⟨?⟩ ɣaǰar‑a 'to the country' and ᠡᠳᠦᠷ ᠡ⟨?⟩ edür‑e 'on the day',[4]: 39  or ᠤᠯᠤᠰ ᠢ⟨?⟩ ulus‑i 'the state' etc.

Orthographic peculiarities are most often retained, as with the short and long teeth of an initial-shaped ⟨ᠥ‍→᠊ᠥ᠌‍⟩ ö in ᠮᠤᠤ‍‍ᠥ᠌‍‍ᠬᠢᠨ Muu'ökin 'Bad Girl' (protective name).

[26][1]: 39 Only in a late form can a definite order of signs be established for the alphabet, but can likely be traced back to an earlier Uyghur model.

g ‍ᠳ᠋‍ In 1587, the translator and scholar Ayuush Güüsh created the Galik alphabet (Али-гали Ali-gali), inspired by the third Dalai Lama, Sonam Gyatso.

It primarily added extra characters for transcribing Tibetan and Sanskrit terms when translating religious texts, and later also from Chinese.

[38] In 1917, the politician and linguist Bayantömöriin Khaisan published the rime dictionary Mongolian-Han Bilingual Original Sounds of the Five Regions,[a] a bilingual edition of the earlier Original Sounds of the Five Regions,[b] to aid Mongolian speakers in learning Mandarin Chinese.

[28]: 535–536 'Pair of dots'[note 25][citation needed] Mongolian numerals are either written from left to right, or from top to bottom.

As exemplified in this section, the shapes of glyphs may vary widely between different styles of writing and choice of medium with which to produce them.

The Mongolian Supplement block (U+11660–U+1167F) was added to the Unicode Standard in June 2016 with the release of version 9.0: The Windows Mongolian traditional script keyboard layout for personal computers is as follows:[57] ᠑ ᠒ ᠓ ᠔ ᠕ ᠖ ᠗ ᠘ ᠙ ᠐ ᠴ č ᠣ o ᠡ e ᠷ r ᠲ t ᠶ y ᠦ ü ᠢ i ᠥ ö ᠫ p 〔 〕 ᠁ ᠠ a ᠰ s ᠳ d ᠹ f ᠭ ɣ/g ᠬ q/k ᠵ ǰ ᠺ g ᠯ l ︔ ᠽ z ᠱ š ᠼ c ᠤ u ᠪ b ᠨ n ᠮ m ᠂ ᠃ !

( ) ᠸ w ᠧ ē ᠿ ž 〈 〉 | ᠾ h ᠻ kh ᡀ lh ᠄ ᡁ zh ᡂ ch ᠩ ng 《 》