It does not make a difference whether you use dry good measuring cups or liquid. It may be EASIER to use liquid measuring cups because you don't have to worry about the liquid overflowing and spilling as you measure, but they both are great! Also, most butter has measurements written on the wrapper.
I assume you are talking about cooking, I have measured it is both, but it is easier to get out of dry ingredient measuring cups. Scientifically speaking peanut butter is not quite a liquid or a solid so you can probably use either.
Measuring liquid.
You're measuring the boiling point of the liquid.
A graduated measuring cylinder
A quart is a measure of liquid.
With a liquid measuring cup
To measure volume of a liquid.
the function of it is to measure all the liquid ingredients
a gratuated cylinder in which you measure the volume of a liquid(volume same as mass)
They are calibrated to water.
If it can measure liquid it is
A measuring cylinder