Learner's definition of SIMPLICITY
the quality of being easy to understand or use
People like the simplicity of the instructions/camera.
For simplicity's sake [=to make it simpler and easier], we have rounded off the numbers to the nearest whole number. = We have rounded off the numbers for the sake of simplicity.
the state or quality of being plain or not fancy or complicated
something that is simple or ordinary but enjoyable
— usually plural
something that is easy to do