What's the verbal expression for 2m ?

2(two) meter.

You place number then add the meter prefix to it :)

Letter b hope it

The major difference is that a histogram is only used to plot the frequency of score occurrences in a continuous data set that has been divided into classes, called bins.  bar charts, on the other hand, can be used for a great deal of other types ofvariables  including  ordinal  andnominal  data sets.