"Romana" refers to two incarnations of the Time Lady Romanadvoratrelundar during her travels with the Doctor. To distinguish the two, they are often referred to as "Romana I" and "Romana II," although the Doctor himself never used those appellations.
Romana I was recruited by what she thought was President Borusa but was in fact the White Guardian, - or, more likely, the Black Guardian posing as his counterpart, - to assist the Fourth Doctor in his quest for the Key to Time. Romana II based her appearance on the Princess Astra and continued travelling with the Doctor before choosing to remain in E-space and help the Tharils in their quest for freedom. In later prose stories in which she returned from E-space and was elected President of the High Council on Gallifrey, Romanadvoratrelundar was generally referred to by her full Gallifreyan name.