knot, knots per hour

Because a knot is a unit of speed equivalent to one nautical mile (1.85 km) per hour, it is redundant to say or write knots per hour.

• The cruising speed of a Boeing 747 is about 490 knots (not knots per hour).
• Winds of up to 75 knots (not knots per hour) are forecast on Lake Michigan.

While it has been traditional to measure the speed of ships, aircraft and wind in knots, the metric (SI) measurement of kilometres per hour is preferred in Canada.

• Even with her sails furled, the Bluenose II can travel at 14.8 km/h (or 8 knots), thanks to her powerful engines.

For the sake of clarity, when knot is used as a modifier, a hyphen is inserted between the numeral and knot (e.g., a 75-knot wind).

• A violent 70-knot gust shredded jibs and mainsails in the Sydney-to-Hobart yacht race.