concentration vs assiduity

concentration and assiduity both are nouns.

Word	Noun	Adjective	Verb	Adverb
concentration	Yes	No	No	No
assiduity	Yes	No	No	No

As nouns, concentration and assiduity are synonyms defined as:

Other synonyms of concentration include assiduousness.

concentration (noun)	assiduity (noun)
strengthening the concentration (as of a solute in a mixture) by removing diluting material	great and constant diligence and attention
bringing together military forces
great and constant diligence and attention
the strength of a solution; number of molecules of a substance in a given volume
the spatial property of being crowded together
complete attention; intense mental effort
increase in density