This chapter is a description of Modern Irish phonology, morphology, syntax and spelling conventions. The evidence provided has been based mainly on material available through linguistic publications since 1900. These publications outline in various detail reliable linguistic descriptions covering phonetic/phonological material, morphological rules and syntactic patterns as well as semantic and sociolinguistic information relating to modern usage. Other materials referred to from time to time cover earlier periods of the language from 1200 onwards. Early Modern Classical Irish had developed and cultivated a standard form of the language for a period of approximately 450 years. This standard language has been described, interpreted and written about in great detail by Ó Cuív (1973, 1980) and McManus (1994a, 1994b) in particular. We are fortunate in having a large body of linguistic material describing all essential elements of this standard language which has survived in manuscript form. This material, termed Irish Grammatical Tracts, was edited and published by Osborn Bergin in a series of supplements in Ériu 8-10, 14, 17 (1916-55).