I know that sodium hydroxide dissociates into sodium cation and hydroxide, so it must be an Arrhenius base. I am also aware of the rule that all Arrhenius acids and bases are considered to be Brønsted-Lowry acids and bases. However, when it comes to sodium hydroxide itself, it seems as if it does not accept proton, but hydroxide does. And someone on this StackExchange stated that it is not a Brønsted-Lowry base, but an Arrhenius base. I am confused now. Is this an exception?