|Era||developed into Middle Polish by the 16th century|
The Polish language started to change after the baptism of Poland, which caused an influx of Latin words, such as kościół "church" (Latin castellum, "castle"), anioł "angel" (Latin angelus). Many of them were borrowed via Czech, which, too, influenced Polish in that era (hence e.g. wiesioły "happy, blithe" (cf. wiesiołek) morphed into modern Polish wesoły, with the original vowels and the consonants of Czech veselý). Also, in later centuries, with the onset of cities founded on German law (namely, the so-called Magdeburg law), Middle High German urban and legal words filtered into Old Polish. Around the 14th or 15th centuries the aorist and imperfect became obsolete. In the 15th century the dual fell into disuse except for a few fixed expressions (adages, sayings). In relation to most other European languages, though, the differences between Old and Modern Polish are comparatively slight; the Polish language is somewhat conservative relative to other Slavic languages.
The difficulty the medieval scribes had to face was attempting to codify the language was the inadequacy of the Latin alphabet to some sounds of the Polish language, for example cz, sz. Thus, Old Polish does not have a standard spelling. One letter could give several sounds - e.g. s can be read as s, sz or ś. Writing words was almost entirely consistent with the spelling of Latin, for example. Bichek - Byczek, Gneuos - Gniewosz etc.
Earliest written sentence
The Book of Henryków (Polish: Księga henrykowska, Latin: Liber fundationis claustri Sancte Marie Virginis in Heinrichau), contains the earliest known sentence written in the Polish language: Day, ut ia pobrusa, a ti poziwai (pronounced originally as: Daj, uć ja pobrusza, a ti pocziwaj, modern Polish: Daj, niech ja pomielę, a ty odpoczywaj or Pozwól, że ja będę mielił, a ty odpocznij, English: Come, let me grind, and you take a rest), written around 1270.
About 1440 Jakub Parkoszowic, a professor of Jagiellonian University, tried to codify the Polish alphabet. He wrote the first tract on Polish orthographic rules (in Latin) and rhyme Obiecado (in Polish). The reform consisted in the introduction of round and unrounded letters on the distinction between hard (velarized) and soft (palatalized) consonants. It also contained merging double vowels to a long vowel, for example: aa – /aː/. Parkoszowic's proposal was not adopted, and his theoretical concepts had no followers.
Over the centuries Old Polish pronunciation was subjected to numerous modifications. These are only the most basic ones.
The consonant system transferred into the soft coronal consonants, for example /tʲ, dʲ, sʲ, zʲ/ for /t͡ɕ, d͡ʑ, ɕ, ʑ/. Many consonant clusters were simplified; which in the process made assimilation reverse many consonants in words, before that following a voiceless consonant.
- The Gniezno Bull (Polish: Bulla gnieźnieńska) a papal bull containing 410 Polish names, published 7 July 1136 (This document can be viewed in Polish wikisource)
- Mother of God (Polish: Bogurodzica) 10th–13th centuries, the oldest known Polish national anthem
- The Book of Henryków (Polish: Księga henrykowska, Latin: Liber fundationis) – contains the earliest known sentence written in the Polish language.
- The Holy Cross Sermons (Polish: Kazania świętokrzyskie) 14th century
- St. Florian's Psalter (Polish: Psałterz floriański) 14th century – a psalmody; consists of parallel Latin, Polish and German texts
- Master Polikarp's Dialog with Death (Polish: Rozmowa Mistrza Polikarpa ze Śmiercią, Latin: De morte prologus, Dialogus inter Mortem et Magistrum Polikarpum) verse poetry, early 15th century
- Lament of the Holy Cross (Polish: Lament świętokrzyski, also known as: Żale Matki Boskiej pod krzyżem or Posłuchajcie Bracia Miła), late 15th century
- Bible of Queen Sophia (Polish: Biblia królowej Zofii), first Polish Bible translation, 15th century
- Ach, Królu wieliki nasz
- Coż Ci dzieją Maszyjasz,
- Przydaj rozumu k'mej rzeczy,
- Me sierce bostwem obleczy,
- Raczy mię mych grzechów pozbawić
- Bych mógł o Twych świętych prawić.
(The introduction to The Legend of Saint Alexius (15th century)