* She was the prettiest girl at the party. (Superlative, comparing her beauty to all other girls at the party)
* This is the prettiest dress I own. (Superlative, comparing it to all her other dresses)
* Of all the flowers in the garden, this rose is the prettiest. (Superlative, specific comparison)
* I think she is the prettiest when she smiles. (Superlative, condition based)
* The mountain view was the prettiest at sunset. (Superlative, time based)