All 5 Uses of

function
in
Red: The Heroic Rescue

He'd fashioned the spyglass from his memory of the histories, using a resin from the pine trees, and although it hardly functioned as he suspected it should, it did give him a slight advantage over the naked eye.†
Chpt 3 *

functioned = worked or operated

The only difference between the Forest People and the Desert Dwellers now was a lake that no longer functioned.†
Chpt 30

In fact, Ciphus of Southern, the Council elder, had calculated that the lakes could function adequately for only three hundred thousand.†
Chpt 1 *

They all seemed to function in it, but to say they controlled it would be wrong, Thomas thought.†
Chpt 8

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.