yardmaster vs railway man

yardmaster and railway man both are nouns.

Word	Noun	Adjective	Verb	Adverb
yardmaster	Yes	No	No	No
railway man	Yes	No	No	No

As nouns, railway man is a hypernym of yardmaster; that is, railway man is a word with a broader meaning than yardmaster:

Other hypernyms of yardmaster include dispatcher, railroad man, railroader, railwayman, trainman.

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