trainman vs yardman

trainman and yardman both are nouns.

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

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

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

trainman (noun)	yardman (noun)
an employee of a railroad	a laborer hired to do outdoor work (such as mowing lawns)
	worker in a railway yard