The quadriceps is the large muscle at the front of your thigh. It is the one you feel when you straighten your knee, stand up from a chair, or climb stairs. Trainers often say “quads” for short. The Latin name means “four-headed,” because this muscle is really four parts that meet near the knee. In the gym, people talk about it as one muscle; in a doctor’s book, it is a group. You meet the word in sport, in injury talk (“I hurt my quadriceps”), and in biology class. At the dinner table, people usually just say “the front of my thigh.”