Showing great care and perseverance : she was assiduous in pointing out every feature.
ORIGIN: mid 16th cent.: from Latin assiduus, from assidere 'be engaged in doing' + -ous .
There are varying degrees of busyness. Busy implies actively and attentively involved in work or a pastime (: too busy to come to the phone). It can also be used to describe intensive activity of any kind (: a busy intersection;: a busy day).
Someone who is engaged is also busy, but in a more focused way (: engaged in compiling a dictionary).
Diligent is used to describe earnest and constant effort, and it often connotes enjoyment of or dedication to what one is doing (: diligent efforts to rescue injured animals).
To be industrious is to be more focused still, often with a definite goal in mind (: an industrious employee working for a promotion).
Sedulous also applies to goal-oriented activity, but it suggests more close care and perseverance than industrious does (: a sedulous investigation of the accident).
The award for concentrated effort goes to the person who is assiduous, which suggests painstaking preoccupation with a specific task (: an assiduous student is the one most likely to win his or her teacher's favor).