associative law
Regrouping a chain of "and"s, or a chain of "or"s, doesn't change its truth value.
The associative laws state that (A ∧ B) ∧ C ≡ A ∧ (B ∧ C) and (A ∨ B) ∨ C ≡ A ∨ (B ∨ C). They do not hold when the connectives are mixed or for the conditional.
Examples
(P ∨ Q) ∨ R and P ∨ (Q ∨ R) have the same truth table.
See also