A piece of equipment that shows how electrical voltage changes, as a line on a screen. A meter only gives you a number; an oscilloscope gives you the shape — a smooth wave, a sharp spike, a flat line that should not be flat. Engineers and repair people use it to see whether a circuit is healthy. Older ones looked like a small green TV with knobs; newer ones look like a laptop. The word is technical: you meet it in labs, workshops, and textbooks, not in everyday chat. Though actually, once you have seen one, the idea is simple — it is just a way of watching electricity move through time, the way a heart monitor watches a heartbeat.