IPA: //əˈsɪdjuːɪti//
KK: /əˈsɪdʒuːɪti/
The quality of being diligent and attentive, showing constant effort and care in tasks or responsibilities.
Her assiduity in studying for the exam paid off with excellent grades.
Assiduity is formed from "assiduus" (meaning sitting near or attending) and the suffix "-ity" (meaning the state or quality of). The word describes the quality of being diligent and attentive, as if one is always present and engaged.
Think of someone who is always 'sitting near' ('assiduus') to their work, showing dedication and diligence — that's what assiduity means.
No commonly confused words.