trainman vs yardmaster

trainman and yardmaster both are nouns.

Word	Noun	Adjective	Verb	Adverb
trainman	Yes	No	No	No
yardmaster	Yes	No	No	No

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

Other hyponyms of trainman include brakeman, signalman, yardman, train dispatcher, trainmaster.

trainman (noun)	yardmaster (noun)
an employee of a railroad	a railroad employer who is in charge of a railway yard