All 4 Uses of

function
in
True Believer, by Sparks

He had seventeen nieces and nephews, and though he sometimes felt out of place at family functions, since he was a bachelor again in a family of happily married people, his brothers were respectful enough not to probe the reasons behind the divorce.
Chpt 2 *

functions = events

Instead, the entire study had simply documented the existence of the lights and the fact that the students' equipment was functioning properly, which barely scratched the surface of the information he needed.
Chpt 2

functioning = working

A steel-gray filing cabinet stood in the corner, and her desk and chair were typically functional.
Chpt 6 *

functional = useful for their purpose

Coincidence accounted for nearly everything else and was simply a function of mathematical probability.
Chpt 10 *

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)
meaning too rare to warrant focus:

For more specialized meanings in math and chemistry, see a comprehensive dictionary.