pursuit vs tailing

pursuit and tailing both are nouns.

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

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

Other hyponyms of pursuit include tracking, trailing, shadowing, stalk, stalking.

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