I’ve learned about them in school, but I’ve never heard anyone say something is 8 decameters long or anything like that. I’m an American.
They are “technically correct” measurements since they are a valid prefix, and could be used if you wanted. but they are very infrequently used in any industry. Since most of the time measurements are better served by higher precision (just using Meters) or need no precision at all over long distance (switch to kilometers), no need for excess measurement types unless necessary
Well he asked about deca and hectometers, which are all larger-than meters.
But the same kind of rules apply below the decimal point as above it. We have millimeters (0.001 extreme precision), centimeters (0.01 high precision), and meters (1 low-ish precision). Decimeters (0.1) exist but are rarely used since both meters and centimeters can get the same result. Micro meters and nanometers are also used more frequently, but it becomes industry specific when actually doing things that small.
Valid, but rarely used, as it’s usually just as fast to say “two hundred meters” instead of “two hecto meters”.
However, those prefixes have other (non-SI) uses. A hectare is common way of referring to a 100x100 meter area. And a decare is 10 ares, i.e. 0.1 hectare.
To be fair, once all the boomers are gone we’re probably going to go full kPa.
For distance, no. Day to day we use mm, cm, m and km. But in more specialised settings (e.g. construction) I’ve seen sometimes decameters.
For weight yes, grams, hectograms, kg, tons. Liquids is usually ml, cl, liters, hectoliters (not sure it’s spelt that way).
In labs I’ve also seen also micro and nano of all three units.
No, some measurements just aren’t used, even when they’d be a good fit.
Like lengths. We never use anything above km. Even for things like space, we say “million km” rather than gigametre.
The closest we come to hectometre is hectare, which is used for land area.
Where do you live and what is your profession? I have heard anyone use megameter seriously.
In The Netherlands we actually use “hectometerpaaltjes”, which translates to hectometer-signs. They are numbered signs placed on regional roads and highways every 100 meters, which is a hectometer. Although not a direct use of measurement, the term hectometer still is in active use this way.
