[R] what does "size" of a plotting character mean?

[Prasenjit Kapat]

Hi,

plot(1,1, cex=2) means that the size of the plotting character (empty
circle in this case) is double the default size. Now my question is:

What characteristic of the symbol (circle) is double? Is it the area
or the diameter?

What if the symbol is not a circle, what is the generic meaning of
size in that case?

Thanks in advance,
PK