I get that usually a- (or un-) and di- prefixes mean different things, e.g. uninterested and disinterested. However, both asymmetric and dissymmetric refer to the lack of symmetry (which the NOAD indicates: “lacking symmetry”). Does that make them freely interchangeable?
Bonus points: why the hell does dissymetry have two s?
Best Answer
You are wrong in the question itself.
So where did the s magically come up from? Well, nowhere - it was there from the beginning, you just messed up the prefix. It's not a di prefix, it's a dis prefix.
Which already answers your question why there are two s in dissymmetry. Well, because there's the prefix + the base:
The same as:
From what I've heard people use the words and also read a few books which contained them, I can say they are synonymous, but dissymmetry is less "famous."