The Only Use

function
in
To Kill a Mockingbird
(Edited)

Jem, educated on a half-Decimal half-Duncecap basis, seemed to function effectively alone or in a group, but Jem was a poor example: no tutorial system devised by man could have stopped him from getting at books.
p. 36.8

function = work

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.