Old High German (OHG, German: Althochdeutsch, German abbr. Ahd.) is the earliest stage of the German language, conventionally covering the period from around 750 to 1050. There is no standardised or supra-regional form of German at this period, and Old High German is an umbrella term for the group of continental West Germanic dialects which underwent the set of consonantal changes called the Second Sound Shift.
At the start of this period, the main dialect areas belonged to largely independent tribal kingdoms, but by 788 the conquests of Charlemagne had brought all OHG dialect areas into a single polity. The period also saw the development of a stable linguistic border between French and German.
The surviving OHG texts were all written in monastic scriptoria and, as a result, the overwhelming majority of them are religious in nature or, when secular, belong to the Latinate literary culture of Christianity. The earliest written texts in Old High German, glosses and interlinear translations for Latin texts, appear in the latter half of the 8th century. The importance of the church in the production of texts and the extensive missionary activity of the period have left their mark on the OHG vocabulary, with many new loans and new coinages to represent the Latin vocabulary of the church.
OHG largely preserves the synthetic inflectional system inherited from Germanic, but the end of the period is marked by sound changes which disrupt these patterns of inflection, leading to the more analytic grammar of Middle High German. In syntax, the most important change was the development of new periphrastic tenses to express the future and passive.
First page of the St. Gall Codex Abrogans (Stiftsbibliothek, cod. 911), the earliest text in Old High German/
Old High German is generally dated, following Willhelm Scherer, from around 750 to around 1050. The start of this period sees the beginning of the OHG written tradition, at first with only glosses, but with substantial translations and original compositions by the 9th century. However the fact that the defining feature of Old High German, the Second Sound Shift, may have started as early as the 6th century and is complete by 750, means that some take the 6th century to be the start of the period. Alternatively, terms such as Voralthochdeutsch ("pre-OHG") or vorliterarisches Althochdeutsch ("pre-literary OHG") are sometimes used for the period before 750. Regardless of terminology, all recognize a distinction between a pre-literary period and the start of a continuous tradition of written texts around the middle of the 8th century.
Differing approaches are taken, too, to the position of Langobardic. Langobardic is an Elbe Germanic and thus Upper German dialect, and it shows early evidence for the Second Sound Shift. For this reason, some scholars treat Langobardic as part of Old High German. But with no surviving texts — just individual words and names in Latin texts — and the speakers starting to abandon the language by the 8th century, others exclude Langobardic from discussion of OHG. As Heidermanns observes, this exclusion is based solely on the external circumstances of preservation and not on the internal features of the language.
The end of the period is less controversial. The sound changes reflected in spelling during the 11th century lead to the remodelling of the entire system of noun and adjective declensions. There is also a hundred-year "dearth of continuous texts" after the death of Notker Labeo in 1022. The mid-11th century is widely accepted as marking the transition to Middle High German.