The universe consists of Space, with an uncountable number of discrete
particles; bodies and masses of material Matter moving in it; during
LENGTH: Is the unit with which we use rulers and tape measures to
determine the cubic measure of volumes; "quantities of space", such as
cubic inches and cubic feet.
FORCE AND WEIGHT: Are the units with which we use balance and weight
scales, to determine _net_ quantities of matter, as pounds and ounces.
Years and Days with subdivisions thereof, such as hours, minutes and
seconds, are the units with which we measure TIME.
So only these three kinds of units make up the three "fundamental
units" of weights and measures.