Irish initial mutations in the context of "Old Irish language"

This is a list of digraphs used in various Latin alphabets. In the list, letters with diacritics are arranged in alphabetical order according to their base, e.g. ⟨å⟩ is alphabetised with ⟨a⟩, not at the end of the alphabet, as it would be in Danish, Norwegian and Swedish. Substantially-modified letters, such as ⟨ſ⟩ (a variant of ⟨s⟩) and ⟨ɔ⟩ (based on ⟨o⟩), are placed at the end.

Capitalisation only involves the first letter (⟨ch⟩ becomes ⟨Ch⟩) unless otherwise stated (⟨ij⟩ becomes ⟨IJ⟩ in Dutch, and digraphs marking eclipsis in Irish, are capitalised on the second letter, i.e. ⟨mb⟩ becomes ⟨mB⟩).

Old Irish, also called Old Gaelic (endonym: Goídelc; Irish: Sean-Ghaeilge; Scottish Gaelic: Seann-Ghàidhlig; Manx: Shenn Yernish or Shenn Ghaelg), is the oldest form of the Goidelic/Gaelic language for which there are extensive written texts. It was used from c. 600 to c. 900. The main contemporary texts are dated c. 700–850; by 900 the language had already transitioned into early Middle Irish. Some Old Irish texts date from the 10th century, although these are presumably copies of texts written at an earlier time. Old Irish is forebear to Modern Irish, Manx and Scottish Gaelic.

Old Irish is known for having a particularly complex system of morphology and especially of allomorphy (more or less unpredictable variations in stems and suffixes in differing circumstances), as well as a complex sound system involving grammatically significant consonant mutations to the initial consonant of a word. Apparently, neither characteristic was present in the preceding Primitive Irish period, though initial mutations likely existed in a non-grammaticalised form in the prehistoric era.

The morphology of Irish is in some respects typical of an Indo-European language. Nouns are declined for number and case, and verbs for person and number. Nouns are classified by masculine or feminine gender. Other aspects of Irish morphology, while typical for an Insular Celtic language, are not typical for Indo-European, such as the presence of inflected prepositions and the initial consonant mutations. Irish syntax is also rather different from that of most Indo-European languages, due to its use of the verb–subject–object word order.