pastime vs pursuit

pastime and pursuit both are nouns.

Word	Noun	Adjective	Verb	Adverb
pastime	Yes	No	No	No
pursuit	Yes	No	No	No

As nouns, pastime and pursuit are synonyms defined as:

pastime and pursuit: a diversion that occupies one's time and thoughts (usually pleasantly)

Other synonyms of pastime include interest.

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

pastime: a diversion that occupies one's time and thoughts (usually pleasantly)
pursuit: an auxiliary activity

Other hyponyms of pastime include avocation, by-line, hobby, sideline, spare-time activity.

pastime (noun)	pursuit (noun)
a diversion that occupies one's time and thoughts (usually pleasantly)	the act of pursuing in an effort to overtake or capture
	a diversion that occupies one's time and thoughts (usually pleasantly)
	an auxiliary activity
	a search for an alternative that meets cognitive criteria