Endings are added to
prefixes
suffixes
roots

Endings are added to roots.

Roots, or also referred to as base words,  are the most basic parts of a word which provide the basic meaning of a word.  The root is a word that does not have a prefix in front of the word or a suffix at the end of the word. A root must have an affix, or another root, attached to it in order to make it a whole word.

what is the question ?

eli whitney was an american inventor best known for inventing the cotton gin. this was one of the key inventions of the industrial revolution and shaped the economy of the antebellum south.