Schwarzian

Schwarzian (plural Schwarzians)

1. (singular only) A particular operator that, when applied to a function f yields a function ${\displaystyle x\mapsto {\frac {f'''(x)}{f'(x)}}-{\frac {3}{2}}\left({\frac {f''(x)}{f'(x)}}\right)^{2}}$
2. (countable) Any image of that operator.

• (both senses): Schwarzian derivative

• Schwarzian on Wikipedia.Wikipedia