Principal Principal
The assets of an account other than income derived from those assets. The specific assets or amounts from which income is earned. (In some cases, the principal may also be referred to as the "corpus" of the trust, and may consist of real estate, stock, personal property, cash and other items which the grantor or donor wished to have included.) In an agency relationship, this word refers to the individual who gives authority to the agent to act on his or her behalf.