If x is initially ambiguous between y and z, can one disambiguate x unto y? or is there a semantically and syntactically similar, more idiomatic, expression?
Let's take an example: "John's green". This could mean "The golf course named after John", "John is new", or "John isn't feeling well". If we say that the context is apprenticeship, then we understand "John's green" to mean "John is new".
Referring to the OP's question (different Lawrence, by the way), one could say that the context of apprenticeship disambiguates the phrase "John's green", specialising it to the meaning "John is new".
3. to render special or specific; invest with a special character, function, etc. - dictionary.com
To my knowledge, "disambiguate" is a grammar term, not a mathematical one. If you are a theoretical mathematician, then I apologize for my lack of knowledge (but I do have mathematics through Dif EQ and Quantum 2). I would use the term "uncertainty," akin to Heisenberg's Uncertainty Principle, where one cannot simultaneously know an electron's location and velocity. The terms "certainty" and its various forms with their corresponding adverbs should solve your problem. Such as: "Initially, there was complete uncertainty in the position of X relative to Y and Z; however, as the function progresses, we see X approaching Y in a predictable fashion."