If you know your Myers-Briggs personality type, you can figure out your dominant and secondary Jungian functions fairly easily.
The first thing you need to know is that only the middle two letters of your type refer to Jungian functions. The 2nd letter (S or N) refers to your main perceiving function and the 3rd letter (T or F) refers to your main judging function.
One of these functions is used primarily in an extraverted way and one is used primarily in an introverted way. In other words, you tend to use one more in the outer world and one more in your inner world. If you are a J, you extravert your judging function and if you are a P, you extravert your perceiving function.
In the example to the right, because the person is a P, the Intuition function (N) is extraverted and thus the Feeling function (F) is introverted. We use the symbols Ne and Fi to indicate this.
The last step is to figure out which one of the two functions is your dominant one. For this we use the 1st letter. If you are an E, your extraverted function will be dominant and if you are an I, your introverted function will be dominant. Here, since the person is an I, the dominant function is Fi (introverted feeling) and the secondary function is Ne (extraverted intuition).
The Jungian notation for INFP would therefore be Fi Ne (the dominant is always listed first). To check whether or not you figured things out correctly for your type, you can refer to the chart on the left.
You’ll notice that if you consider only the dominant functions, the 16 types turn into only 8 types. These 8 types were the original psychological types that Carl Jung developed, years before Isabel Myers and Katharine Briggs developed the Myers-Briggs system.
Finally, here is a chart describing each of the eight Jungian functions and what they do: