This is the 14197th most frequent Russian word.
оригинальная
Original.
In this instance, "оригинальная" describes the idea as 'distinctive and novel,' emphasizing originality in thought or concept.
Идея была необычной и оригинальной.
The idea was unusual and original.
In this sentence, "оригинальная" means 'referring to something unique or distinct, not an iteration or copy', describing the quality of the book as being original.
Она прочитала оригинальную книгу.
She read an original book.
Here, "оригинальная" conveys 'referring to creativity or uniqueness,' applied to the costume to indicate its distinctiveness.