Viscosity, which can be seen as the partner of friction, is the “measure of how hard it is for one layer of fluid to slide over another layer.”1 If a liquid is hard to move it is more viscous. If it is more viscous there is more resistance. Viscosity isn’t usually an issue for humans in our day-to-day lives. We have to deal with gravity and inertia, although viscosity is always present. But for small particles, gravity and inertia become a nonissue compared to viscosity. So if you make things bigger, viscosity is less relevant.
