A bodysuit is a single piece of clothing. If it's two separate pieces of clothing, such as a leotard over a pair of pantyhose, then it's not a bodysuit.
A bodysuit usually covers the whole body, from neck to toe. Some bodysuits may only cover the upper arms or legs, but this is the exception, not the rule. If it doesn't cover the arms at all, it's a sleeveless bodysuit. If it doesn't cover the arms or legs at all, like a one-piece swimsuit, then it's a leotard instead.
A bodysuit is usually made of sturdy material and worn by itself. If it's made of sheer or thin material, like pantyhose, then it's a bodystocking instead. If it's worn beneath other clothing, then it's probably not a bodysuit (unless it's a bodysuit under clothes).
