Newtonian refers to the scientific work of Isaac Newton, in particular:

• Newtonian mechanics, also known as classical mechanics
• Newtonian telescope, a type of reflecting telescope
• Newtonian cosmology
• Newtonian fluid, a fluid that flows like water—its shear stress is linearly proportional to the velocity gradient in the direction perpendicular to the plane of shear
  • Non-Newtonian fluids, in which the viscosity changes with the applied shear force