Pitiful, piteous, pitiable are comparable but not always interchangeable when they mean arousing or deserving pity or compassion.
Pitiful applies especially to what actually excites pity or, sometimes, commiseration because it is felt to be deeply pathetic. But pitiful may apply to something meriting pity or commiseration less as pathetic than as contemptible, especially in its inadequacy.
Piteous implies not so much an effect on the observer as a quality in the thing that excites pity; thus, a cry is piteous if it implores or demands attention or pity; it is pitiful only if it actually excites pity; one may scorn a piteous appeal, but it would be a contradiction in terms to scorn a pitiful appeal.
Pitiable (see also CONTEMPTIBLE ) may be preferred to pitiful when a contemptuous commiseration is implied, but contempt may be weakly or strongly connoted.