Limct;
I have seen the terms used interchangeably in reporting of fatigue test data for ferrous (steels) material, so I would have to say they mean the same thing.
As a follow-up, for some non-ferrous material where the S (stress amplitude)/N (cycles) graph does not flatten beyond a certain number of cycles, the endurance limit of 10^8 cycles is specifically used to define the fatigue strength for the material.
As a follow-on to metengr, I would add that the flattenning of the S/N cyrve is characteristic of materials which strain harden, such as carbon steel. This is due to the interstitial-dislocation interaction arresting the dislocation propagation which would otherwise lead to failure.
