Wry neck, or torticollis, is a painfully twisted and tilted neck. The top of the head generally tilts to one side while the chin tilts to the other side. This condition can be congenital (present at birth) or acquired. It can also be the result of damage to the neck muscles or blood supply. Wry neck sometimes goes away without treatment.
In the quaternions, 0 is the additive identity. In the ring of functions from R to R, the function mapping every number to 0 is the additive identity. In the additive group of vectors in Rn, the origin or zero vector is the additive identity.
Inverse - Additive Inverse. The additive inverse of a number, a, is the number, -a, you add to it to get 0 (the additive identity). a + (-a) = 0. Examples: The additive inverse of 8 is -8 since 8 + (-8) = 0. The additive inverse of -2 is 2 since -2 + 2 = 0. Inverse - Multiplicative Inverse. The multiplicative inverse of a number, a, is the number, 1/a, that you multiply it to so you get 1 (the multiplicative identity). Example: The multiplicative inverse of 5 is 1/5. The multiplicative inverse of 1/2 is 2.