juror vs petty juror

juror and petty juror both are nouns.

Word	Noun	Adjective	Verb	Adverb
juror	Yes	No	No	No
petty juror	Yes	No	No	No

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

Other hyponyms of juror include foreperson, petit juror, juryman, jurywoman.

juror (noun)	petty juror (noun)
someone who serves (or waits to be called to serve) on a jury	a member of a petit jury