Variables accessible in unrelated files?

Currently, on my computer, I have two Matlab files. One is saved to my desktop and one is saved to my documents folder. I see no reason why these two .m files should be able to access one another. Here is the code for the first .m file which is saved to my documents folder.

syms R

rstatic = .5; 
comp = .5; 
targetVolume = (4/3)*(pi)*(.5)^3; 
startingCircumfrence = 2*pi*(.5);

%Preliminary Equations 
d = rstatic + (R - comp); 
a = (1/d)*((4*(d^2)*(R^2))-((d^2)-(rstatic^2)+(R^2))^2)^(1/2); 
z = ((rstatic^2) - (((1/2)*a)^2))^(1/2); 
capHeight1 = (rstatic - z); 
capHeight2 = (comp - capHeight1); 
capVol1 = ((pi*(capHeight1)^2)/3)*((3*rstatic)-capHeight1);
capVol2 = ((pi*(capHeight2)^2)/3)*((3*R)-capHeight2); 
removedVolume = (capVol1 + capVol2); 

%Volume Expansion 
deformedVol = ((4/3)*(pi)*(R^3)) - removedVolume == targetVolume;

radiusFromExpansion = vpasolve(deformedVol,R,[.5 Inf]); 
circumfrenceFromExpansion = (2*pi*radiusFromExpansion); 

%Return the values 
radiusFromExpansion  %#ok<NOPTS>
circumfrenceFromExpansion   %#ok<NOPTS> 

Somehow, in the .m file that is saved to my desktop, I am able to call circumfrenceFromExpansion. The entirity of the desktop file is

circumfrenceFromExpansion  

Can someone explain to me how this is possible and what I can do to prevent this? The two projects are unrelated and ideally I would like to reuse variable names.