Notation to give units in legend/axis label/etc

Question

When writing e.g. an axis label for a plot or a header for a table column that contains data that is associated with a unit (e.g. a length in meters), I always used to write it down like this:

length [m]

until someone told me that the proper notation for this would be

length / m

indicating that you have "divided away" the unit for the provided data (which is then unitless). The reason, I was told , why the latter is to be preferred is that the square brackets are usually used as some kind of operator that returns the unit of the quantity it is acting on, e.g.

[length] = m

Now, I am wondering whether this is indeed the general consenus in physics (or if everybody does this to their own preference) and if it is, does this kind of notation have some kind of name that I could refer to when talking about this?

Answer 1

This is of course a subjective issue, but for what it's worth, both PRL and Nature use axes that are labelled as Quantity (unit), see PRL style guide and Nature extended formatting guide.

For what it's worth, I've written documents with axes labelled with quantity / unit or quantity [unit], and have never gotten in trouble for it.

I think it's more important to be consistent throughout a document and, even more importantly, to make figures readable (large enough font, discernible colors (also for colorblind folks or for black/white printouts), no cluttering of the figure with too much text boxes, etc.). If you use a decent software, it should be possible to set default values for axes labels and such so that you can easily conform to whatever standard a professor, a journal, or somebody else demands.