the 15th century, with the accretion of Norse and English loan words, the
Scottish branch differed significantly enough from the Irish to warrent
definition as a separate language. And nowadays these two tongues
though having very much in common in vocabulary and grammar, are different.
The alphabets of Irish and Scottish Gaelic are indentical, consisting of 18 letters. Scottish employs four cases of nouns: nominative, genitive, dative and vocative (Irish uses three). Like Irish, the accent is usually on the initial syllable.
Scottish Gaelic exists in two main dialects, Northern and Southern, geographically determined by a line roughly up the Firth of Lorne to the town of Ballachulish and then across to the Grampian Mountains, which it follows northeasterly. The Southern dialect is more akin to Irish than is the Northern, and is more inflected. The main difference is the change of the Indo-European é sound, which is eu in the Northern dialect and ia in the Southern. Thus the word for "grass" is pronounced feur in Northern and fiar in Southern. But most linguists can find many more varieties of the language, each having its own peculiarities. In fact, Scottish Gaelic is endangered today by the permanent expansion of English and Scots both. Only on the islands to the west can people be found who speak only Gaelic. On the mainland everyone understands English and slowly their native tongue is lost to them.