A survival knife, IMO, is any knife that you carry ALL THE TIME. "Survival" situations are the textbook definition of Murphy's Law and survival situations usually occur when you aren't geared down for the adventure. For example when I go on hikes, extended Kayak trips, etc I take my Fällkniven F1 and an Estwing Hatchet (because you really don't want to put the stress of chopping or batoning on a knife if you don't have to even if its capable) along with my EDC Leatherman Skelatool, multiple firesteels, tinder, food, plenty of water for the expected duration, water purification tabs, etc, but lets face it, although its possible, that's not when things are likely to turn into survival mode because I'm well prepared beyond the scope of my planned adventure. When things are most likely to turn into a survival setting is when an unexpected event happens or when you think you are only going "off the grid" for an hour or so and don't pack or plan for an extended adventure. This scenario, the true survival scenario, leaves you with only the stuff you have with you and your ability to make that stuff work for you, therefore if you buy a knife that's going to sit at home until you plan a trip and pack it, it's most likely not going to be with you in a survival situation.