Alternate and Substitute Parts

When somebody asks, what is the difference between Alternate Part and Substitute Part? We always get confused. Hence I am putting definitions for each.

Alternate Part:

An Alternate Part is a component that is a suitable replacement for another part in every assembly in which the original part occurs. Companies use alternate parts when multiple vendors can supply parts that serve the identical function and fit.

 

Substitute Part:

A substitute part is a component that is a suitable replacement for another part in only one assembly in which the original part occurs.