railyard vs piece of land

railyard and piece of land both are nouns.

Word	Noun	Adjective	Verb	Adverb
railyard	Yes	No	No	No
piece of land	Yes	No	No	No

As nouns, piece of land is a hypernym of railyard; that is, piece of land is a word with a broader meaning than railyard:

railyard: an area having a network of railway tracks and sidings for storage and maintenance of cars and engines
piece of land: an extended area of land

Other hypernyms of railyard include parcel, parcel of land, piece of ground, tract.

railyard (noun)	piece of land (noun)
an area having a network of railway tracks and sidings for storage and maintenance of cars and engines	an extended area of land