sister
sorelle
soh-REL-lah
Sorellina (little sister) and fratellino (little brother) are affectionate diminutives used for younger siblings. Sorellastra (stepsister) and fratellastro (stepbrother) indicate half or step relationships.
Mia sorella studia medicina all'università.
My sister studies medicine at university.
Le due sorelle si assomigliano moltissimo.
The two sisters look very alike.