promotion vs preferment

promotion and preferment both are nouns.

Word	Noun	Adjective	Verb	Adverb
promotion	Yes	No	No	No
preferment	Yes	No	No	No

As nouns, preferment is a hyponym of promotion; that is, preferment is a word with a more specific, narrower meaning than promotion:

Other hyponyms of promotion include ennoblement, investiture, investment.

promotion (noun)	preferment (noun)
act of raising in rank or position	the act of preferring
the advancement of some enterprise	the act of making accusations
a message issued in behalf of some product or cause or idea or person or institution
encouragement of the progress or growth or acceptance of something