ITEM IDENTIFICATION able pattern with a refractory slurry that sets at room temperature. After this, the wax, plastic, or frozen mercury pattern is removed through the use of heat. This procedure is also known as precision casting or the lost wax process. ION An atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more elec- trons. IRRADIATION The exposure of a material to high-energy emis- sions. In insulations, for the purpose of favorably altering the molecular structure. ISOKERAUNIC (or Isoceraunic) Showing equal frequency of thunderstorms. ISOLATION Physical and electrical arrangement of the parts of an equipment, system, or facility to prevent uncontrolled electrical contact within or between the parts. ISOTROPIC Having uniform properties in all directions. The mea- sured properties of an isotropic material are independent of the axis of testing. ISSUING AGENCY CODE (IAC) The IAC represents the regis- tration authority that issued the enterprise identifier. ITEM (1) A nonspecific term used to denote any unit or product including materials, parts, assemblies, equipment, accessories, and computer software. (2) A single hardware article or a single unit formed by a grouping of subassemblies, components, or constituent parts. (3) A general term used to denote any unit of product or data, including materials, parts, assemblies, equipment accessories, computer software, or documents that have entity. ITEM, COMMERCIAL An item designed and available for pur- chase on the commercial market and included in the term item, pri- vately developed. ITEM DESCRIPTION (NOMENCLATURE) The name and description of an item as it appears in the contract, purchase order, or requisition. The source document for this information is the DD Form 61 (Request for Nomenclature), which contains the exact name and description of an item. ITEM, END An item in the assembled or completed state at which Government procurement takes place. ITEM IDENTIFICATION (1) The combination of the part or identifying number and the original design activity CAGE code. (2) The part or identifying number or descriptive identifier for a spe- 153