What do the letters in the Myers-Briggs test stand for?

What do the letters in the Myers-Briggs test stand for? Each MBTI personality type consists of 4 letters. The first letters are either E or I, the second letter is either an S or an N, the third will either be a T or an F, and the last letter will either be a J or a P.

The sixteen Myers-Briggs personality types

What Is MBTI: Myers-Briggs 16 Personalities Test & Types

What is the Myers-Briggs Type Indicator (MBTI)?

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Myers-Briggs Type Indicator - What do the letters mean?

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What exactly do the letters in the 16 personalities stand for and signify? - Quora