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When I wanted to use word 'measure' in the past I used 計測 or 測る. But recently
I got a message from a Japanese co-worker:

> 申し訳ありません  
>  18時前にネット障害がおこり最後の **計測** できませんでした...  
>  まだ復旧してないので明日18時に **測定** します

I understand what it says, but I am a little confused as to the difference
between 計測 and 測定. Would it be correct if I used 計測 in the last sentence too?
When do people use one over the other?
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2021-01-16T00:37:03.863
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meaning kanji nouns business-japanese
What is the difference between 計測 and 測定?
It appears to me the reason for choosing 「測定」in the last sentence may very
well have been something to do with 「定」. See [goo
辞書](https://dictionary.goo.ne.jp/word/kanji/%E5%AE%9A/#jn-149026):

> 物事を決めて変えない。さだめる。さだまる。

This kanji has the meaning of "making certain", "determine", "to firmly
establish", "to get fixed".「測定」means to determine the value of something
accurately. So when they talk about when it is possible to get an outcome, to
establish the value, they picked 「測定」. 「計測」just means to measure with tools.
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2021-01-16T01:03:30.043
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While they both can translate "to measure", there is a slight difference. Even
among dictionaries, there are difference in definition, so I am using the
[Japan Industrial Standard
definition](https://kikakurui.com/z8/Z8103-2019-01.html).

測定{そくてい} means to measure against a standard (unit) and obtain data.  
計測{けいそく} means to use data from obtained through measurement and process it to
obtain a result for a certain purpose.

So 計測 includes 測定 within its definition. You can think of 測定 as the simple
measurement, whereas 計測 are more complex measurement that uses data obtained
from 測定. An example would be measuring weight (測定) vs measuring BMI (計測）.

That being said, most Japanese speakers would not be able to explain the
difference off the top of their head (I couldn't), so using one in place of
the other isn't going to be the end of the world.
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answer