2020-10-27
ศัพท์ น่าสับสน ชุด K - Knot
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Dictionary.com
ออกเสียง knot = ‘NOT’
Abused, Confused, & Misused Words by Mary Embree
knot
cord, rope, ribbon, or the like that is tied or folded upon itself;
a tangle in hair; a difficulty: a knotty problem
Not to be confused with:
not – expressing negation, denial, or prohibition: I will not answer your question.
Collins English Dictionary
Word History:
In nautical usage, knot is a unit of speed, not of distance,
and has a built-in meaning of "per hour."
A ship is said to travel at ten knots (and not ten knots per hour).
Although the knot is defined as one nautical mile per hour,
the similarityin sound between knot and nautical mile is entirely coincidental.
The unit calledthe knot originated in a traditional method of measuring the speed of ships in use at least since the 16th century. A long rope was knotted at fixed intervals, wound on a spool, and tied to the end of a large wooden wedge, called the chip log orjust log. When the log was thrown into the water, it would remain in roughly the same place where it splashed down. As the ship moved away,the rope would pay out and sailors would count the number of knots in the rope that were paid out over a fixed stretch of time, usually measured with a sand hourglass. Eventually, the calculation of speed using this methodwas made easier by knotting the rope at intervals of 47 feet and 3 inches and using an hourglass that ran out after 30 seconds. If one knotin the rope was paid out during this time, the ship was said to be moving at one knot, or one nautical mile per hour. Because of adjustments in the standard values of units of measurement over the years, a 28-second interval of time is now used in calculating a ship's speed using a rope in this way, but the basic principle remains the same.
Dictionary of Problem Words and Expression
Knot
It is an error to mention “knots an hour” or “knots per hour.”
A knot in this sense refers to a unit of speed, “1 nautical mile an hour.”
Consequently, the word knot should never be followed by an hour.
A ship can travel “at 10 knots” or “at 10 nautical mile an hour,”
but not “at 10 knotsan hour.”
Nor can a ship “cover such and such a number of knots.”
It speeds(or crawls) at so many knots and covers so many nautical miles in a day.
Merriam-Webster Dictionary
Usage Notes
Is 'Knots an Hour' Wrong?
Some say knots can only be a measure of speed. Are they right?
Ah, that salty breeze blowing over the water!
Let's say we sail over to yonder small island and check it out.
To know how long it'll take us to get there, we of course need to know how far away it is and how fast we'll be going. We'll measure distance in nautical miles (each of which is equivalent to 1.15 statute miles or 1852 meters, and some portion of which is used in both sea and air navigation), and we'll measure speed using … knots?
Yes, knots. A knot is one nautical mile per hour.
Here's the background on that: Originally ships used log lines with literal knots in them to measure speed. Just like the knots, the log lines were also literal, sort of. Line is the sailor's word for rope (rope can get you thrown overboard), and the log was actually a pie-shaped flat piece of wood(from a log) with a lead weight on the curved edge so that it would float upright. A line with knots about every 47 feet was attached to the "log." The log was tossed overboard and would stay more or less where it landed, while the attached log line would continue trailing out from the ship. After 28 seconds as measured by the sandglass, the number of knots that had passed overboard was counted and the resulting number was the speed of the ship.
(An aside: the speed of the vessel was noted in the book about the goings-on of the log line, aka the "logbook." Logbook got shortened to log,and the log itself was used to record everything about a ship's voyage. Log latercame to apply to the full record of a flight by an aircraft, and then to any of various kinds of records of performance, events, or day-to-day activities. When people started chronicling their lives and thoughts online, the word weblog referred to the sites they used and the content they wrote, and was later shortened to blog.)
But back to our journey: we're traveling nautical miles and we're measuring our speed in knots. Our island is fictional, and we don't actually own a boat, but knots are real. And possibly confusing. Our imagined vessel has an electronic device that gives us lots of information including our speed, so we don't need any knotted lines trailing behind us, but when the instrument reports "12" do you say "We're traveling 12 knots" or "We're traveling 12 knots an hour"?
Well, nautically (and strictly) speaking, a knot is a unit of speed equal to one nautical mile per hour, and a vessel is described as traveling at (or "making") a certain number of knots. But occasionally sentences like "We're traveling 12 knots an hour" are heard. In such cases, the word knot doesn't mean"nautical miles an hour." It means simply "nautical miles."
Those in the know do not appreciate such uses, and you might want to avoid it with your sailor friends and frenemies. But if you do happen to say "knots an hour" or "knots per hour" and some seafaring (or word-watching) type implies that it's an offense worthy of plank-walking, you may feel free to point out that this meaning of knot was first entered in a dictionary in 1864, and that it was first recorded a century earlier in the writings of two people who knew their way around a gunwale:
… the ship went ten knots an hour with a prodigious sea....
— Admiral George Anson, Anson's Voyage Round the World, 1748
… we were at that time running at the rate of six knots an hour….
— Captain James Cook, Voyages, 1790
Usage continued by others with some experience of the nautical life:
When the ship was running nine knots an hour, these animals [porpoises] could cross and recross the bows with the greatest of ease, and then dash away right ahead.
— Charles Darwin, The Voyage of the Beagle, 1839
We were gliding along, hardly three knots an hour….
— Herman Melville, Mardi: And a Voyage Thither, 1849
All of which is to say: those who say "knots an hour" instead of "knots" are in pretty good company—and not just the company of landlubbers.
