Both languages take their origin from the language of the Gaels. The Gaels are a people who settled in Ireland from mainland Europe. After settling in Ireland they later moved to Scotland and the Isle of Man. In a similar fashion to how Latin splintered into a number of different languages after the fall of Rome the languages of the Gaels changed as they moved east from Ireland in the 6th and 7th century.
A dialect or a language?
There are some disputes as to whether or not Irish and Scottish Gaelic are different languages or if they are simply different dialects of the same language. The distinction between a language and a dialect is typically drawn at the point when speakers can no longer understand each other. The general consensus however is that Irish Gaelic and Scottish Gaelic has enough differences to be considered a different language. Visually both languages look similar in the same way that visually Spanish and Portuguese share similarities. But when spoken they sound very different and there is certainly enough differences to consider them different languages.
What’s in a name?
A point of confusion for those who aren’t overly familiar with the languages is that they both share the same name. They are both Gaelic languages in the sense that they share their roots from the language of the Gaels. But the common term used when talking about Irish Gaelic in Ireland is simply Irish. Rarely, if ever, will you hear someone in Ireland referring to the language as Irish Gaelic. The word Gaelic is also pronounced very differently in both countries with the Irish pronouncing the word like GAY-lik and the Scottish pronouncing it like GAA-lik.
This is a major difference with the two languages. While both languages do have a lot of words in common they sound very different. Some native Irish speakers, especially those from the more northern parts of the country like Donegal, can understand a greater volume of Scottish Gaelic. As this area of Ireland is geographically closer to Scotland it meant historically there was a great dialogue between the two regions which leads to the great understanding.
But for the most part Irish speakers cannot understand Scottish Gaelic. While the language still shares a lot of the same sounds in the most part they are very different.
Another big give away when spotting the differences between the two languages is the use of accent marks. At one point both languages used both right-slanting and left-slanting accents. However as the languages have evolved accent marks always slant to the right in Irish and to the left in Scottish Gaelic. A good example of this is how the welcome is written in each language. In Irish the word is written fáilte
while in Scottish Gaelic the word is written fàilte.
There are also a lot of major spelling differences in both languages. A lot of this stems from the reform and simplification of Irish spelling which started in the 1950’s. This eliminated a lot of silent consonant combinations in Irish that Scottish Gaelic has kept. You can see a number of examples of this below.
Irish enjoys constitutional status as the national and first language of the Republic of Ireland. The official language of Scotland is English.