a member of the Goidelic group of Celtic languages, spoken in Ireland. As one of the national languages of the Republic of Ireland, Irish is taught in the public schools and is required for certain civil-service posts.

Grammatically, Irish still has a case system, like Latin or German, with four cases to show differing functions of nouns and pronouns in a sentence. In phonology it exhibits initial sandhi, in which the first consonant of a word is modified according to the prehistoric final sound of the previous word in the phrase (e.g., an tobar “the well,” mo thobar “my well”).

Records in the Irish language date back to the ogham (ogham writing) inscriptions, written in sets of strokes or notches, of the 5th century AD; the Latin alphabet began to be used shortly thereafter. Irish literature dates from the 8th century. See also ogham writing; Celtic languages.