Prōne'ness, n.

n. 1. The state of being prone, or of bending downward; as, the proneness of beasts that look downward, opposed to the erectness of man.

2. The state of lying with the face downward; — opposed to supineness.
3. Descent; declivity; as, the proneness of a hill.
4. Inclination of mind, heart, or temper; propension; disposition; as, proneness to self-gratification or to self-justification; the proneness of good men to commiserate want.