In my study material, there is a chart of the fundamental units. In that solid angle and angle are separated by a line from the other fundamental units. What is the reason for that?


closed as primarily opinion-based by John Rennie, GiorgioP, Kyle Kanos, HDE 226868, stafusa Jun 16 at 21:40

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    $\begingroup$ You'd have to ask the author why they laid out the table like that. One possible reason is that angles are dimensionless because they are defined as ratios. $\endgroup$ – John Rennie Jun 4 at 6:05
  • $\begingroup$ @JohnRennie isn't any unit defined as a ratio? $\endgroup$ – santimirandarp Jun 4 at 8:37
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    $\begingroup$ @santimirandarp no, e.g. the unit of length like 1 m is not a ratio: it's actual length of a reference object. $\endgroup$ – Ruslan Jun 4 at 9:54

My guess that it's to separate them from fundamental physical units. You can think of an angle of 5000 degrees or maybe an angle of 1,000,000 radians, they may be interpreted as rotation of how ever many rotations, but in either case they are not a fundamental (physical) units such as mass, force etc..


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