Gàidhealtachd
The Gàidhealtachd /kɛːəɫtaxk/ (Eng: Gaeldom), sometimes known as A' Ghàidhealtachd (Eng: the Gàidhealtachd), usually refers to the Scottish highlands and islands, and especially the Scottish Gaelic culture of the area. The corresponding Irish word Gaeltacht however refers strictly to an Irish speaking area. The term is also used to apply to the Gaelic-speaking areas of Nova Scotia, Canada.
The term the Gàidhealtachd is not truly interchangeable with the term highlands, as it refers to the culture and not to the geography. Also, many parts of the highlands no longer have substantial Gaelic-speaking populations, and some parts of what is now thought of as the highlands have traditionally been Scots-speaking areas: Caithness, Cromarty, Grantown-on-Spey, Campbeltown etc. Conversely, several Gaelic-speaking communities lie outwith the Highland, Argyll and Bute and Western Isles council areas, for example Arran and parts of Perth and Kinross. For this reason, the Gàidhealtachd also increasingly refers to the regions in Scotland and Nova Scotia where Scottish Gaelic is spoken as the native language by most or some part of the population.
Galldachd (Gall-dom, Gall referring to a non-Gael; cognate with Gaul) is often used for the Lowlands, although it is also notable that the Hebrides are known as Innse Gall due to the historical presence of Norsemen.
History
In the past, the Gàidhealtachd would have included much of modern day Scotland outside the extreme south east and the Northern Isles, as evidenced by the prevalence of Gaelic derived place names throughout Scotland, and contemporary accounts. These include Dundee from the Gaelic Dùn Deagh, Inverness from Inbhir Nis, Stirling from Sruighlea, Argyll from Earra-Ghàidheal and Galloway from Gall-Ghaidhealaibh. Gaelic speakers from what would be considered traditionally English speaking/non-Gaelic regions today included George Buchanan from Stirlingshire, and Robert the Bruce and Margaret McMurray from Galloway and Ayrshire.
For historical reasons, including the influence of a Scots-speaking royal court in Edinburgh, and the plantation of merchant burghs in much of the south and east, the Gàidhealtachd has been reduced massively to the present region of the Western Isles, and the North-West Highlands, Skye and Lochalsh and Argyll and Bute, with small Gaelic populations existing in Glasgow and Edinburgh.
Canadian Gàidhealtachd
Scottish Gaelic has also survived among communities descended from immigrants in parts of Nova Scotia (especially Cape Breton Island), Prince Edward Island and Newfoundland in eastern Canada and those areas where Gaelic is spoken can also be said to be Gàidhealtachdan.