topic vs precedent

topic and precedent both are nouns.

Word	Noun	Adjective	Verb	Adverb
topic	Yes	No	No	No
precedent	Yes	Yes	No	No

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

Other hyponyms of topic include bone of contention, head, question, keynote.

topic (noun)	precedent (noun)
some situation or event that is thought about	an example that is used to justify similar occurrences at a later time
the subject matter of a conversation or discussion	(civil law) a law established by following earlier judicial decisions
	a subject mentioned earlier (preceding in time)
	a system of jurisprudence based on judicial precedents rather than statutory laws

topic (adjective)	precedent (adjective)
	preceding in time, order, or significance