Pentland Firth (pĕntˈlənd fûrth) [key], channel, 6 to 8 mi (9.7–12.9 km) wide and c.14 mi (23 km) long, N Scotland. Connecting the North Sea with the Atlantic Ocean, it separates the Scottish mainland from the Orkney Islands. Its rough waters have proven dangerous to small vessels. Small islands dot the Pentland Firth.
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