relating to or produced by or consisting of molecules; "molecular structure"; "molecular oxygen"; "molecular weight is the sum of all the atoms in a molecule"
impossible or difficult to perceive by the mind or senses; "an imperceptible drop in temperature"; "an imperceptible nod"; "color is unperceivable to the touch"
either of two bean-shaped excretory organs that filter wastes (especially urea) from the blood and excrete them and water in urine; "urine passes out of the kidney through ureters to the bladder"