erratic vs quicksilver

erratic is not a noun while quicksilver is a noun.

Word	Noun	Adjective	Verb	Adverb
erratic	No	Yes	No	No
quicksilver	Yes	Yes	No	No

As adjectives, erratic and quicksilver are synonyms defined as:

Other synonyms of erratic include fickle, mercurial.

erratic (noun)	quicksilver (noun)
	a heavy silvery toxic univalent and bivalent metallic element; the only metal that is liquid at ordinary temperatures

erratic (adjective)	quicksilver (adjective)
liable to sudden unpredictable change	liable to sudden unpredictable change
likely to perform unpredictably
having no fixed course