Subalternation is an immediate inference which is only made between A (All S are P) and I (Some S are P) categorical propositions and between E (No S are P or originally, Not every S is P) and O (Some S are not P or originally, No S is P) categorical propositions of the traditional square of opposition and the original square of opposition. If the...
• (n.) The state of being subalternate; succession of turns; subordination.
Sub·al'ter·na`tion noun The state of being subalternate; succession of turns; subordination. 
subalternation The state of being subalternate; succession of turns; subordination.
See Logic, formal, § 4.