f'f′(x)
is read
- f prime of x, or
- the derivative of f of x, or
- the derivative of f with respect to x.
f''f″(x)
is read
- f double prime of x, or
- the second derivative of f of x, or
- the second derivative of f with respect to x.
ẋ
is read
- x dot, or
- the derivative of x with respect to time, or
- the time derivative of x.
If x is a distance, ẋ can also be read as the x component of the velocity.
If x is a distance, and is also the only direction of motion, ẋ can also be read as speed or velocity.
ẍ
is read
- x double dot, or
- the second derivative of x with respect to time.
If x is a distance, ẍ can also be read as the x component of the acceleration. If x is a distance, and is also the only direction of motion, ẍ can also be read as acceleration.