예쁘다 is the dictionary form of pretty, and "예쁘" is the stem. In order to use 예쁘다 we must conjugate it. To conjugate it we must take "~다" away from the stem and conjugate the stem. It can be conjugated into: 예뻐 (casual/informal), 예뻐요 (polite/casual), 예쁩니다 (formal). We can also use 예쁘다 without conjugating it, but that will also be considered casual/informal.

예쁘다 is the dictionary form of pretty, and "예쁘" is the stem. In order to use 예쁘다 we must conjugate it. To conjugate it we must take "~다" away from the stem and conjugate the stem. It can be conjugated into: 예뻐 (casual/informal), 예뻐요 (polite/casual), 예쁩니다 (formal). We can also use 예쁘다 without conjugating it, but that will also be considered casual/informal.