Maybe you'll find this to be of help: he difference between a symbol and a sign is that a symbol can convey a deeper and more complex meaning than a sign. A sign is an indicator or marker for something very specific, very concrete and, in general, unambiguous in meaning. Road markers are called signs because they usually convey something very specific - the speed limit, "Stop", a street name, etc. There is nothing open to interpretation with these markers (except in the minds of some lawyers, perhaps :-) ). On the other hand a symbol, whether a cross, a dove, a ring, etc. can have a complex meaning and nuance that differs from one person to another depending on their experience, culture, upbringing, schooling, and so on. A symbol conveys a message of deeper meaning and is open to interpretation. A picture containing a dove could be meant to convey a message about peace, or it could be a picture of a bird. A ring worn on the finger could mean a commitment to another person in marriage, and marriage itself means different things to different people, but it may also be just a piece of jewellery. So the "$" is called a dollar sign, not a dollar symbol, because has a quite distinct and concrete meaning. It represents a unit of currency, however, it doesn't mean any unit of currency but very specifically the unit of currency known as the dollar. So, a "sign" is some unit of communication that represents something specific, while a "symbol" is a unit of communication imbued with deeper and more complex meaning. Mark comes closer to character than symbol or sign, because it carries little, if any, suggestion of reference to an idea. It is the ordinary designation of any of various characters that are used to make clear the meaning of a passage but that add nothing to that meaning or that indicate to the eye how words should be pronounced.

they can all be a little similar but different in some contexts. A mark is to scratch, tag, write or stain something etc. A symbol is usually a shape used to identify something. A sign is usually giving you some information about something.