10 C.F.R. § 490.301
In addition to the definitions found in section 490.2 , the following definitions apply to this subpart-
Affiliate means a person that, directly or indirectly, controls, is controlled by, or is under common ownership or control of a person subject to vehicle acquisition requirements in this part.
Alternative Fuels Business means activities undertaken to derive revenue from-
Business Unit means a semi-autonomous major grouping of activities for administrative purposes and organizational structure within a business entity and that is controlled by or under control of a person subject to vehicle acquisition requirements in this part.
Division means a major administrative unit of an enterprise comprising at least several enterprise units or constituting a complete integrated unit for a specific purpose and that is controlled by or under control of a person subject to vehicle acquisition requirements in this part.
Normal Requirements and Practices means the operating business practices and required conditions under which the principal business of a person subject to vehicle acquisition requirements in this part operates.
Principal Business means the sales-related activity that produces the greatest gross revenue.
Substantial Portion means that at least 30 percent of the annual gross revenue of a covered person is derived from the sale of alternative fuels.
Substantially Engaged means that a covered person, or affiliate, division, or other business unit thereof, regularly derives more than a negligible amount of sales-related gross revenue from an alternative fuels business.
10 C.F.R. §490.301