Is curling the fingers considered digit flexion?

Question

Is curling the fingers considered finger flexion and straightening the fingers considered finger extension? I feel like this is correct in everyday language, but I am not sure if it is correct in anatomical terms.

Answer 1

In the vertical plane, bending of the fingers is indeed referred to as flexion, while straightening is called extension. In the horizontal plane, spreading the fingers is called abduction, and approximation is called adduction (Fig. 1).

^{Fig. 1. Finger movements and terminology. source: US Dept. of Veteran Affairs}