The Collaborative International Dictionary
noninterchangeable
noninterchangeable \noninterchangeable\ adj.
(math, logic) not able to be interchanged without changing the truth value.
Not able to be substituted for each other; -- of objects, such as parts of machinery; as, the ink cartidges on the new printer are noninterchangeable with those on the older model.
Wiktionary
noninterchangeable
a. That cannot be interchanged with another
WordNet
noninterchangeable
adj. such that the terms of an expression cannot be interchanged without changing the meaning; "the arguments of the symmetric relation, `is the father of', are noninterchangeable"