Define one second Define one kg mass. Define one solar day

One second - One second is the time that elapses during 9,192,631,770 (9.192631770 x 10 to the 9th power) cycles of the radiation produced by the transition between two levels of the cesium 133 atom.

One kg mass - the mass of a particular international prototype made of platinum-iridium and kept at the International Bureau of Weights and Measures. It was originally defined as the mass of one liter (10^-3 cubic meter) of pure water. At the Earth's surface, a mass of 1 kg weighs approximately 2.20 pounds (lb)

One solar day - the time between successive meridian transits of the sun at a particular place

Unclear