slightness vs pettiness

slightness and pettiness both are nouns.

Word	Noun	Adjective	Verb	Adverb
slightness	Yes	No	No	No
pettiness	Yes	No	No	No

As nouns, slightness and pettiness are synonyms defined as:

slightness and pettiness: the quality of being unimportant and petty or frivolous

Other synonyms of slightness include puniness, triviality.

slightness (noun)	pettiness (noun)
slenderness	the quality of being unimportant and petty or frivolous
the property of an attractively thin person	lack of generosity in trifling matters
the quality of being unimportant and petty or frivolous	narrowness of mind or ideas or views