In a natural object the following are similar but distinct: substance, essence, nature, form, species. The knowledge of these is the concept, which is expressed fully in the definition and symbolized by the common name. Since man cannot create substance but can merely fashion substances that are furnished by nature, an artificial object such as a chair has t wo essences: the essence of its matter (wood, iron, marble, etc.) and the essence of its form (chair). The essence of the form is expressed in the definition (of chair). Frequently, a common name symbolizes a concept that is not simple nor equivalent to the essence of the natural species, like human being, but is a composite, like lawyer or athlete, including in its definition certain accidents which determine not natural species but classes that differ only accidentally. A composit e concept may be called a construct. Lawyer and athlete are constructs, for their definition adds to the simple concept human being certain accidents such as knowledge of law or physical agility, which are essential to the definition of lawyer or of athlete although not essential to the definition of a construct. For example, a particular lawyer may be tall, blond, irritable, generous, etc., but these accidents are not more essential to being a lawyer than they are to being a human being. A const ruct may be analyzed into its components by showing in what categories its essential meanings lie.