Complex sentence: Philippa Plantagenet, (16 August 1355--5 January 1382), Countess of Ulster "sui juris", was the daughter and only child of Lionel of Antwerp, 1st Duke of Clarence and Elizabeth de Burgh, 4th Countess of Ulster.
Split into simpler sentences: Philippa Plantagenet, (16 August 1355--5 January 1382), Countess of Ulster "sui juris". She was the daughter and only child of Lionel of Antwerp, 1st Duke of Clarence and Elizabeth de Burgh, 4th Countess of Ulster.