What is transferred between species during an acid-base reaction?

1. An acid-base reaction is defined by the movement of H+ from one species to another. 2. When HCl dissolves, H+ moves from HCl to a water molecule to give H3O+. 3. When ammonia dissolves, H+ moves from water to NH3 to give NH4+ and OH-. 4. Movement of electrons instead defines an oxidation-reduction reaction. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_