All 5 Uses

function
in
The Longest Ride
(Edited)

The room was functional and unpretentious, devoid of trophies or awards or laminated articles.
p. 216.7 *

functional = useful for its purpose
The kitchen was small and functional, with inexpensive cabinets.
p. 250.5
The house needed a new roof, and the kitchen and bathrooms, though functional, were not to Ruth's liking.
p. 267.5

functional = useful for their purpose
I mean, we both know that art history majors are absolutely critical to the modern functioning of society.
p. 337.5

functioning = properly working
The fact that he didn't win in Macon wasn't a reflection of how well he rode, but rather a function of the quality of the bulls.
p. 371.1 *

function = result

Definitions:

(1) (function as in: Its main function is to...)
purpose, job, or natural activity
(2) (function as in: can't function well without sleep)
work or operate -- sometimes to work or operate normally or in a particular way
(3) (function as in: I'm attending a function tonight)
a social event or ceremony -- especially one attended for work or out of a sense of duty
(4) (function as in: oxygen is a function of altitude)
saying one results from another; or saying that the amount of one thing is dependent upon the value of another.

If x is a function of y, then x results from y; or the amount of x can be calculated based on the amount of y.
(5) (function as in: Amazon's new search function)
computer code that performs a specific task
(6) (function as in: a mathematical function)
a formula or mathematical expression that describes a relationship between variables
(7) (meaning too rare to warrant focus)
For more specialized meanings in math and chemistry, see a comprehensive dictionary.