90-
Method of igntion.
It is: 79-38 = 41
It is 52 - 38 = 14.
14.6341% difference.
It depends. Many people say "38" when they are referring to the .38 special, so in that case, there is no difference, they are one and the same. However, there are several .38 caliber cartridges other than the .38 special. There is the .38 ACP, .38 long Colt, .38 short Colt, .38 S&W, .38 Super, and I think one or two others.
Bullet diameter on a 38 is .357; on a 380 it is .355 Case is longer on a 38.
If you mean +P, the difference is velocity.
The difference between 38 and 72 is calculated by subtracting 38 from 72, which equals 34. This means that 72 is 34 units greater than 38. In terms of their relationship on a number line, 38 is to the left of 72, and the gap between them is 34.
It depends on what you mean. A .38 revolver may be a .38 special, but there are other types of .38 besides just the special round.
+P has more muzzle velocity
The .38 Special is a specific cartridge. In addition to the .38 Special, there are perhaps a dozen different .38 cartridges. Most of them are fairly obscure/ obsolete today, but include the shorter, fatter, less powerful .38 S&W, the .38 Long and Short Colts, the .38 rimfires, .38 Merwin & Hullbert, etc. Sort of like "What is the difference between a Ford Mustang and a Ford?"
though they have one similarity both have the difference of 38