HCl: Hydrochloric acid, a strong acid that dissociates in water to produce hydrogen ions (H+) and chloride ions (Cl-).
HF: Hydrofluoric acid, another compound containing the same fluoride ion but bonded with hydrogen instead of sodium. It has different properties from NaF.
Solution: A homogeneous mixture where one substance called the solute dissolved completely into another substance called the solvent.