If something's piteous, it makes you feel pity and concern. The piteous cries of the orphaned kittens under your porch might convince you to climb under there and gather them up so you could feed them.
Use the adjective piteous when you want to describe something that deserves your feelings of compassion and sympathy. A baby's cry, a miserable facial expression, and a pleading voice can all be piteous if they make you feel bad and want to help. The root word of piteous is the Latin pietas, meaning dutiful conduct or compassion. In Medieval Latin, it became pietosus and meant both merciful and pitiful.