as ‧ sid ‧ u ‧ ous /əˈsɪdjuəs $ -dʒuəs/ BrE AmE adjective formal
[ Date: 1500-1600 ; Language: Latin ; Origin: asiduus , from assidere ; ⇨ ↑ assess ]
very careful to make sure that something is done properly or completely SYN meticulous
assiduous in
He was assiduous in his attendance at church.
—assiduously adverb :
Even young children worked assiduously for a reward.
—assiduity /ˌæsəˈdjuːəti, ˌæsɪˈdjuːəti $ -ˈduː-/ noun [uncountable]