The crossword solution for the term PRINCIPLE PART is BODY, which has four letters. The BODY is the main part of a person or animal, and it is composed of many different organs and systems that work together to keep the organism alive and functioning. It is also the physical form of a person or animal, and it is the part of the organism that can be seen and touched. In addition, the BODY is the foundation of the mind and spirit, and it is the source of physical strength and energy.