There are many times when we can use different words to describe the same thing and, as long as the reader or listener has the same understanding of meaning, they are synonyms. It’s a bit like “text-speak” where abbreviations abound and you sometimes need to read a passage aloud for it to make sense; spelling and punctuation becomes an individual preference. But there are cases where correct spelling and punctuation is important and, for example, a mis-placed comma can change the meaning of a sentence. (I recommend “Eats, Shoots & Leaves” by Lynne Truss as further reading for anyone interested in following this up.)
We often talk about “signs and symbols” or “signs and symptoms” as though the three words, sign, symptom and symbol are interchangeable – and, in common usage this need not be an issue. However, there are significant differences that can become important in gaining a clear understanding. You can look the words up in whatever dictionary you have to hand and there will probably be a degree of overlap in definitions. My simplification:
Sign: an object or feature that points to the presence of something else.
Symbol: a mark or character that represents something else. Like a sign, it points but, specifically, it is a representation.
Symptom: a feature that indicates the presence of something else. Similar to sign except that is usually refers to a disease or problem and, specifically, the symptoms are experienced by the affected body (internal, whereas the signs will be sensed externally).
So, you may ask, with the overlap, why are the differences important? My answer has to be that, in most cases, they aren’t and that sign is a good all-encompassing word. However, there are situations where we need to be more specific and symbol and symptom tell us more. We need to recognise those times and ensure we use the correct term.