Substitute part—a part that possesses such functional and physical characteristics as to be capable of being exchanged with the design part only under specified conditions or in particular applications without alteration of the parts themselves or adjoining items. Substitute parts should be reviewed and approved in accordance with PMP requirements.
Alternate part—a part that possesses functional and physical characteristics as to be equivalent in performance, reliability, and maintainability to an original design part without selection for fit or performance. An alternate part should be subject to the same part selection review and approval process as the original design part and should be included on the BOM.
Superseding part—a part deemed desirable for use as a replacement part for the original design part (which becomes the superseded part). A superseding part meets all requirements of an alternate part, but is used exclusively in lieu of the original design part.

Substitute part - равнозначный/тождественный
Alternate part - взаимозаменяемый
Superseding part - идентичный

Вы хоть определение прочтите (for use as a replacement part for the original design part)