We measure things like length, width, height, mass, volume and temperature in units. There are two general systems, metric and imperial. I grew up in a time when I went through high school entirely using imperial. My brother a year behind me used half imperial and half metric. The brother a year behind him was all metric. We are seriously messed up.
But it’s not just us. Measurement in Canada is messy and confusing. We still measure weight in pounds and ounces, height in feet and inches, distance in time to get there. See the chart at the right for how it “works”.
If in Canada, we’re supposed to use the metric system, why don’t we use all of it? When was the last time you referred to a dekameter or a decimeter? A recent news report said there was 900 mm of rain. Seems like a lot and it is, but not 900 worth. Why would rain storm water depth be measured as 900 millimetres vs 90 centimetres or 9 decimetres or 0.9 metres? Does it mean to make it sound bigger? Why don’t we use the 
whole metric system instead of cherry picking a few parts of it?
It seems to me, if we’re truly going to be a metric nation, we should in fact use the whole system. Not me though, my mind till mostly thinks in imperial measurements. I will confess that, occasionally, I think that cold temperatures make a little more sense in Celsius. True, I may have gone too far with that.