train set vs plaything

train set and plaything both are nouns.

Word	Noun	Adjective	Verb	Adverb
train set	Yes	No	No	No
plaything	Yes	No	No	No

As nouns, plaything is a hypernym of train set; that is, plaything is a word with a broader meaning than train set:

train set: a toy consisting of small models of railroad trains and the track for them to run on
plaything: an artifact designed to be played with

Other hypernyms of train set include toy.

train set (noun)	plaything (noun)
a toy consisting of small models of railroad trains and the track for them to run on	an artifact designed to be played with