1. adjective
a) Pertaining to a fraction.
2. noun
a) An expression of a fractional number.
In English, most ordinals double as fractionals — "third", "fourth", and so on — with the exception of "second", whose corresponding fractional is "half".
b) Partial ownership of a property, such as real estate or a chartered airplane, such that each partial owner has use of the property for only a portion of the time.
A fractional is much more expensive than a traditional timeshare, but to many people, its worth it.
Wikipedia foundation.