Firth is a word in theEnglish andScots languages used to denote various coastal waters in theUnited Kingdom, predominantly withinScotland. In theNorthern Isles, it more often refers to a smallerinlet. It is linguisticallycognate to Scandinavianfjord andfjard (all fromProto-Germanic *ferþuz), with the original meaning of "sailable waterway". The word has a more constrained sense in English. Bodies of water named "firths" tend to be more common on the Scottish east coast, or in the southwest of the country, although theFirth of Clyde is an exception to this. TheHighland coast contains numerous estuaries, straits, and inlets of a similar kind, but not called "firth" (e.g.the Minch andLoch Torridon); instead, these are often calledsea lochs. Before about 1850, the spelling "Frith" was more common.
A firth is generally the result ofice ageglaciation and is very often associated with a large river, where erosion caused by the tidal effects of incoming sea water passing upriver has widened the riverbed into anestuary. Demarcation can be rather vague. TheFirth of Clyde is sometimes thought to include the estuary as far upriver asDumbarton, but theOrdnance Survey map shows the change from river to firth occurring offPort Glasgow. In navigation terms, the dredged River Clyde Channel for shipping meets the Firth of Clyde Channel at theTail of the Bank, where the river crosses asandbar offGreenock as the estuary widens at the junction to theGare Loch. Locally, the river can be described as extending even further west toGourock point.
However, some firths are exceptions. TheCromarty Firth on the east coast of Scotland, for example, resembles a largeloch with only a relatively small outlet to the sea and theSolway Firth and theMoray Firth are more like extremely large bays. ThePentland Firth is astrait rather than a bay or an inlet.
InScottish Gaelic, the Firth of Clyde is treated as two bodies, with the landward end being calledLinne Chluaidh (IPA:[ˈʎiɲəˈxl̪ˠuəj]; meaning the same as the English), while the area around the south of Arran, Kintyre and Ayrshire/Galloway isAn Linne GhlasScottish Gaelic pronunciation:[əˈʎiɲəˈɣl̪ˠas̪].
Cliffs in Saviskaill Bay onRousay, looking northward toWestray across Westray Firth
The Northern Isles were part of Norway until the 15th century, and retain many Norse names. In Shetland in particular, "firth" can refer to smaller inlets, althoughgeo,voe andwick are as common. In Orkney, "wick" is common.
Likewise, in theNorthern Isles, the words "firth" and "sound" are often used arbitrarily or interchangeably.Bluemull Sound for example, is very similar to some of the firths in theShetland Islands.
^Anderson, Joseph (Ed.) (1893)Orkneyinga Saga. Translated by Jón A. Hjaltalin & Gilbert Goudie. Edinburgh. James Thin and Mercat Press (1990 reprint).ISBN0-901824-25-9
