unambiguous

An expression is called "well-defined" (or "unambiguous") if its definition assigns it a unique interpretation or value. Otherwise, the expression is said to not be well-defined or to be ambiguous. For example, the expression a b c (the product) is well-defined if a, b, and c are integers. Because integers are associative, a b c has the same value whether it is interpreted to mean (a b) c or a(b c). However, if a, b, and c are Cayley numbers, then the expression a b c is not well-defined, since Cayley numbers are not, in general, associative, so that the two interpretations (a b) c and a(b c) can be different.

ambiguous | ill-defined | undefined