Ambivert

A person near the middle of the extraversion scale.
What it is
Researchers score extraversion on a continuum with introversion at one end, so many people sit between the ends, and the word ambivert is sometimes used for them. It describes a position on a scale and not a separate kind of person.
In effect
In the article on the difference between introverts and extroverts, it shows why a continuum leaves room for people near the middle.
What it does not say
It is a label for a position on a scale, not a type or a diagnosis.
Sources
- Lucas, R. E., Diener, E., Grob, A., Suh, E. M., & Shao, L. (2000). Cross-cultural evidence for the fundamental features of extraversion. Journal of Personality and Social Psychology, 79(3), 452-468.