Section 21.1 - Applicability and definitions(a) This part prescribes-(1) Procedural requirements for issuing and changing-(ii) Production approvals;(iii) Airworthiness certificates; and(iv) Airworthiness approvals;(2) Rules governing applicants for, and holders of, any approval or certificate specified in paragraph (a)(1) of this section; and(3) Procedural requirements for the approval of articles.(b) For the purposes of this part-(1)Airworthiness approval means a document, issued by the FAA for an aircraft, aircraft engine, propeller, or article, which certifies that the aircraft, aircraft engine, propeller, or article conforms to its approved design and is in a condition for safe operation, unless otherwise specified;(2)Article means a material, part, component, process, or appliance;(3)Commercial part means an article that is listed on an FAA-approved Commercial Parts List included in a design approval holder's Instructions for Continued Airworthiness required by § 21.50 ;(4)Design approval means a type certificate (including amended and supplemental type certificates) or the approved design under a PMA, TSO authorization, letter of TSO design approval, or other approved design;(5)Interface component means an article that serves as a functional interface between an aircraft and an aircraft engine, an aircraft engine and a propeller, or an aircraft and a propeller. An interface component is designated by the holder of the type certificate or the supplemental type certificate who controls the approved design data for that article;(6)Product means an aircraft, aircraft engine, or propeller;(7)Production approval means a document issued by the FAA to a person that allows the production of a product or article in accordance with its approved design and approved quality system, and can take the form of a production certificate, a PMA, or a TSO authorization;(8)State of Design means the country or jurisdiction having regulatory authority over the organization responsible for the design and continued airworthiness of a civil aeronautical product or article;(9)State of Manufacture means the country or jurisdiction having regulatory authority over the organization responsible for the production and airworthiness of a civil aeronautical product or article.(10)Supplier means a person at any tier in the supply chain who provides a product, article, or service that is used or consumed in the design or manufacture of, or installed on, a product or article.Doc. No. FAA-2006-25877, Amdt. 21-92, 74 FR 53384, Oct. 16, 2009; Doc. No. FAA-2013-0933, Amdt. 21-98, 80 FR 59031, Oct. 1, 2015; Amdt. 21-98A, 80 FR 59031, Dec. 17, 2015; Docket FAA-2015-0150, Amdt. 21-99, 81 FR 42207, June 28, 2016; Docket FAA-2018-1087, Amdt. 21-105, 86 FR 4381, Jan. 15, 2021