Complex sentence: An accumulation of pus enclosed in tissue space is known as an abscess, while a visible collection of pus within or beneath the epidermis is known as a pustule or pimple.
Split into simpler sentences: An accumulation of pus in an enclosed tissue space is known as an abscess. A visible collection of pus within or beneath the epidermis, on the other hand, is known as a pustule or pimple.