period of play vs quantity

period of play and quantity both are nouns.

Word	Noun	Adjective	Verb	Adverb
period of play	Yes	No	No	No
quantity	Yes	No	No	No

As nouns, quantity is a hypernym of period of play; that is, quantity is a word with a broader meaning than period of play:

period of play: (in games or plays or other performances) the time during which play proceeds
quantity: how much there is or how many there are of something that you can quantify

Other hypernyms of period of play include amount, measure.

period of play (noun)	quantity (noun)
(in games or plays or other performances) the time during which play proceeds	how much there is or how many there are of something that you can quantify
	an adequate or large amount
	the concept that something has a magnitude and can be represented in mathematical expressions by a constant or a variable