concentration vs assiduousness

concentration and assiduousness both are nouns.

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

As nouns, concentration and assiduousness are synonyms defined as:

concentration and assiduousness: great and constant diligence and attention

Other synonyms of concentration include assiduity.

concentration (noun)	assiduousness (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