Definition:Alpha-Formula

Definition
Let $\mathbf A$ be a WFF of propositional logic that is not a literal.

Then $\mathbf A$ is an $\alpha$-formula iff either:


 * $\mathbf A = \neg \neg \mathbf A_1$

for some WFF $\mathbf A_1$, or:


 * $\mathbf A$ is semantically equivalent to a conjunction $\mathbf A_1 \land \mathbf A_2$

for some WFFs $\mathbf A_1, \mathbf A_2$.