BTW ... you say: > Maybe it's just a too advanced paper for my knowledge. Maybe it is for now ... the point being that if you start at the beginning, chip awa

BTW ... you say: > Maybe it's just a too advanced paper for my knowledge. Maybe it is for now ... the point being that if you start at the beginning, chip away at it, search for terms on the 'net, read multiple times, try to work through it, and then ask people when you're really stuck, that's one way of making progress. You can, instead, enroll in an on-line course, or night-school, and learn all this stuff from the ground up, but it will almost certainly take longer. Your knowledge would be better grounded and more secure, but learning how to read, investigate, search, work, then ask, is a far greater skill that "taking a course". Others have answered your specific question about the delta symbol, but there are deeper processes/problems/questions here: * Not all concepts or values or represented by a single glyph, sometimes there are multi-glyph "symbols", such as "Δt" in your example. * When you see a symbol you don't recognise, read the surrounding text. The symbol will almost always be referenced or described. * The notation isn't universal. Often it's an aid to your memory, to write in a succinct form the thing that has been described elsewhere. * In these senses, it's very much a language more akin to natural languages than computer languages. The formulas are things used to express a meaning, not things to be executed. * Specific questions about specific notation can be answered more directly, but to really get along with mathematical notation you need to "read like math" and not "read like a novel". * None of this is correct, all of it is intended to give you a sense of how to make progress.