The Lenore Thomson Exegesis Wiki
A function-attitude is a Jungian function used in an Extraverted or Introverted attitude.
In Lenore's system, there are four functions:
Sensation
Intuition
Thinking
Feeling
...and eight function-attitudes:
Extraverted Sensation
Extraverted Intuition
Extraverted Thinking
Extraverted Feeling
Introverted Sensation
Introverted Intuition
Introverted Thinking
Introverted Feeling
Lenore often refers to function-attitudes just as "functions", which goes back to Jung.
On this wiki, we lean toward the more intuitively clear word "attitudes".
Exactly what a function-attitude is is the main part of the Definition Problem. See also Genus Problem.
See Rational and Irrational for a systematic breakdown of the function-attitudes in an unusual way.
Q. Why did Jung choose the term "function"?
A. Jung, Psychological Types, p.273: He borrow terms coined by Otto Gross. The "primary function" and the "secondary function".
A. He probably called it a function because it is a function! A function is an action performed by something, in this case a brain! It makes perfect sense.
A. Random House definition of function: #1 the kind of action or activity proper to any person or thing #2 the purpose for which something is designed or exists. As an INFJ, it makes perfect sense to me. Your function is what serves your purpose, it is what's proper to yourself. If you want more of where this came from, check this out