Both Uses

function
in
Flowers for Algernon -- Short Story
(Edited)

Under separate cover I am sending you a copy of my report entitled, "The Algernon-Gordon Effect: A Study of Structure and Function of Increased Intelligence," which I would like to have you read and have published.
p. 17.3

function = activity
Yet for the sake of science, I am grateful for the little bit that I here add to the knowledge of the function of the human mind and of the laws governing the artificial increase of human intelligence.
p. 17.5 *

function = natural activity

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.