Question: when can you say that a set is well defined

title: Well-defined
text: In mathematics , an expression is called well - defined or unambiguous if its definition assigns it a unique interpretation or value . Otherwise , the expression is said to be not well - defined or ambiguous . A function is well - defined if it gives the same result when the representation of the input is changed without changing the value of the input . For instance if f takes real numbers as input , and if f ( 0.5 ) does not equal f ( 1 / 2 ) then f is not well - defined ( and thus : not a function ) . The term well - defined is also used to indicate whether a logical statement is unambiguous . 

Answer: answer: In mathematics, an expression is called well-defined or unambiguous if its definition assigns it a unique interpretation or value.
The term well - defined is also used to indicate whether a logical statement is unambiguous.