substitutivity
/ˌsʌbstɪtjuːˈtɪvɪti/ /ˌsʌbstɪtʃuːˈtɪvɪti/Logic
noun
The capacity of terms to function as equivalent substitutes for one another within a statement, without causing loss of truth.
Origin
1930s; earliest use found in W. V. Quine (1908–2000), philosopher. From substitutive + -ity.